The ß- radio-guided surgery: Method to estimate the minimum injectable activity from ex-vivo test.

PURPOSE: Radio-guided surgery with ß- decays is a novel technique under investigation. One of the main advantages is its capability to detect small (⩽0.1 ml) samples after injecting the patient with low activity of radiopharmaceutical. This paper presents an experimental method to quantify this feature based on ex-vivo tests on specimens from meningioma patients. METHODS: Patients were enrolled on the basis of the standard uptake value (SUV) and the tumour-to-non-tumour activity ratio (TNR) resulted from 68Ga-DOTATOC PET exams. After injecting the patients with 93-167 MBq of 90Y-DOTATOC, 26 samples excised during surgery were analyzed with a ß- probe. The radioactivity expected on the neoplastic specimens was estimated according to the SUV found in the PET scan and the correlation with the measured counts was studied. The doses to surgeon and medical personnel were also evaluated. RESULTS: Even injecting as low as 1.4 MBq/kg of radiotracer, tumour residuals of 0.1 ml can be detected. A negligible dose to the medical personnel was confirmed. CONCLUSIONS: Radio-guided surgery with ß- decays is a feasible technique with a low radiation dose for both personnel and patient, in particular if the patient is injected with the minimum required activity. A correlation greater than 80% was observed between the measured counts and the expected activity for the lesion samples based on the individual SUV and the TNR. This makes identifiable the minimum injectable radiotracer activity for cases where 90Y is the utilized radionuclide.

First ex vivo validation of a radioguided surgery technique with ß-radiation.

PURPOSE: A radio-guided surgery technique with ß(-)-emitting radio-tracers was suggested to overcome the effect of the large penetration of γ radiation. The feasibility studies in the case of brain tumors and abdominal neuro-endocrine tumors were based on simulations starting from PET images with several underlying assumptions. This paper reports, as proof-of-principle of this technique, an ex vivo test on a meningioma patient. This test allowed to validate the whole chain, from the evaluation of the SUV of the tumor, to the assumptions on the bio-distribution and the signal detection. METHODS: A patient affected by meningioma was administered 300MBq of (90)Y-DOTATOC. Several samples extracted from the meningioma and the nearby Dura Mater were analyzed with a ß(-) probe designed specifically for this radio-guided surgery technique. The observed signals were compared both with the evaluation from the histology and with the Monte Carlo simulation. RESULTS: we obtained a large signal on the bulk tumor (105cps) and a significant signal on residuals of ∼0.2ml (28cps). We also show that simulations predict correctly the observed yields and this allows us to estimate that the healthy tissues would return negligible signals (≈1cps). This test also demonstrated that the exposure of the medical staff is negligible and that among the biological wastes only urine has a significant activity. CONCLUSIONS: This proof-of-principle test on a patient assessed that the technique is feasible with negligible background to medical personnel and confirmed that the expectations obtained with Monte Carlo simulations starting from diagnostic PET images are correct.

Feasibility of simultaneous sodium fluorescein and indocyanine green injection in neurosurgical procedures.

OBJECTIVE: The objective of this study is to assess the feasibility of simultaneous Sodium Fluorescein (SF) and Indocyanine Green (ICG) injection during neurosurgical procedures. PATIENTS AND METHODS: Three patients harboring a high-grade glioma (HGG) were retrospectively identified in the surgical database of the Neurosurgical Unit 2 at the Foundation IRCCS Istituto Neurologico C. Besta in Milan, by having received intraoperatively both SF for tumor resection and ICG for vasculature angiographic studies in the same surgical procedure. We identified 2 males and 1 female (age range 25-60). Lesions were located in the left temporo-polar area and hippocampus (1 case), right superior frontal gyrus (1 case), left supplementary motor area (1 case). All the three lesions showed Magnetic Resonance Imaging (MRI) characteristics of HGG and, for this reason, in all patients a fluorescein-guided tumor removal was proposed. In the same surgical procedure ICG videoangiography was considered necessary in order to study arterial and venous vasculature, given by the strict relation of the tumor with an unexpected Posterior Communicating Artery (PComA) aneurysm in one case and with cortical drainage veins complexes in the other two cases. In all cases a microscope equipped with both YELLOW560 and IR800 integrated filters (Pentero 900, Carl Zeiss, Oberkorchen, Germany) was used. Fluorescein was i.v. injected at a dose of 5mg/kg immediately after patient intubation. ICG was i.v. injected in bolus on demand of the operating surgeon at a dose of 12.5mg. RESULTS: No side-effects related to simultaneous injection of SF and ICG were identified. In all three cases, the use of SF allowed to better visualize the tumor areas during surgical removal, thus leading to a radical resection until no macroscopic appearance of residual tumor mass and no fluorescence was visible in the surgical cavity. ICG videoangiography confirmed the patency of branches of internal carotid artery after clipping of an unexpected small PComA aneurysm found intraoperatively during tumor removal in one case, while in patient 2 and 3 it allowed to evaluate patency and study flow pattern in cortical drainage veins that were intimately related to the tumors and the way of the surgical approach. Postoperative MRI showed a Gross Total Resection of the tumors in all cases. CONCLUSIONS: This study showed for the first time the feasibility of intravenous SF injection and ICG videoangiography in the same surgical procedure. The presence of different fluorescence filters on the same surgical microscope allows the surgeon to recognize and safely resect the tumor and simultaneously evaluate local brain vascularization.

Long-term results of a randomized controlled trial analyzing the role of systematic pre-operative coronary angiography before elective carotid endarterectomy in patients with asymptomatic coronary artery disease.

OBJECTIVES: To evaluate the potential benefit of systematic preoperative coronary-artery angiography followed by selective coronary-artery revascularization on the incidence of myocardial infarction (MI) in patients undergoing carotid endarterectomy (CEA) without a previous history of coronary artery disease (CAD). METHODS: We randomised 426 patients who were candidates for CEA, with no history of CAD, a normal electrocardiogram (ECG), and a normal cardiac ultrasound. In group A (n = 216) all patients underwent coronary angiography before CEA. In group B (n = 210) CEA was performed without coronary angiography. Patients were not blinded for relevant assessments during follow-up. Primary end-point was the occurrence of MI at 3.5 years. The secondary end-point was the overall survival rate. Median length of follow-up was 6.2 years. RESULTS: In group A, coronary angiography revealed significant coronary artery stenosis in 68 patients (31.5%). Among them, 66 underwent percutaneous Intervention (PCI) prior to CEA and 2 received combined CEA and coronary-artery bypass grafting (CABG). Postoperatively, no MI was observed in group A, whereas 6 MI occurred in group B, one of which was fatal (p = .01). During the study period, 3 MI occurred in group A (1.4%) and 33 were observed in group B (15.7%), 6 of which were fatal. The Cox model demonstrated a reduced risk of MI for patients in group A receiving coronary angiography (HR,.078; 95% CI, 0.024-0.256; p < .001). In addition, patients with diabetes and patients <70 years presented with an increased risk of MI. Survival analysis at 6 years by Kaplan-Meier estimates was 95.6 ± 3.2% in Group A and 89.7 ± 3.7% in group B (Log Rank = 6.54, p = .01). CONCLUSIONS: In asymptomatic coronary-artery patients, systematic coronary angiography prior to CEA followed by selective PCI or CABG significantly reduces the incidence of late MI and increases long-term survival. (ClinicalTrials.gov number, NCT02260453).

A novel radioguided surgery technique exploiting ß(-) decays.

The background induced by the high penetration power of the radiation is the main limiting factor of the current radio-guided surgery (RGS). To partially mitigate it, a RGS with ß(+)-emitting radio-tracers has been suggested in literature. Here we propose the use of ß(-)-emitting radio-tracers and ß(-) probes and discuss the advantage of this method with respect to the previously explored ones: the electron low penetration power allows for simple and versatile probes and could extend RGS to tumours for which background originating from nearby healthy tissue makes probes less effective. We developed a ß(-) probe prototype and studied its performances on phantoms. By means of a detailed simulation we have also extrapolated the results to estimate the performances in a realistic case of meningioma, pathology which is going to be our first in-vivo test case. A good sensitivity to residuals down to 0.1 ml can be reached within 1 s with an administered activity smaller than those for PET-scans thus making the radiation exposure to medical personnel negligible.

Diagnostic accuracy of 320-row computed tomography as compared with invasive coronary angiography in unselected, consecutive patients with suspected coronary artery disease.

Noninvasive coronary angiography with multislice computed tomography (CT) scanners is feasible with high sensitivity and negative predictive value. The radiation exposure associated with this technique, however, is high and concerns in the widespread use of CT have arisen. We evaluated the diagnostic accuracy of coronary angiography using 320-row CT, which avoids exposure-intensive overscanning and overranging. We prospectively studied 118 unselected consecutive patients with suspected coronary artery disease (CAD) referred for invasive coronary angiography (ICA). All patients had 320-row CT within 1 week of ICA, which, together with quantitative analysis, served as the reference standard. Of the 65 out of 118 patients who were diagnosed as having CAD by ICA, 64 (98 %) were correctly identified at 320-row CT. Noteworthy, 320-row CT correctly detected CAD in 3 patients with atrial fibrillation and ruled out the disease in the other 8 patients. From 151 significant coronary stenoses detected on ICA, 137 (91 %) were correctly identified with 320-row CT. In the per-patient analysis, sensitivity and specificity of 320-row CT were 98 and 91 %, respectively. In the per-vessel analysis, sensitivity and specificity of 320-row CT were 93 and 95 %, respectively. In the per segment analysis, sensitivity and specificity of 320-row CT were 91 and 99 %, respectively. Diameter stenosis determined with the use of CT showed good correlation with ICA (P < 0.001, R = 0.81) without significant underestimation or overestimation (-3.1 ± 24.4 %; P = 0.08). Comparison of CT with ICA revealed a significantly smaller effective radiation dose (3.1 ± 2.3 vs. 6.5 ± 4.2 mSv; P < 0.05) and amount of contrast agent required (99 ± 51 vs. 65 ± 42 ml, P < 0.05) for 320 row CT. The present study in an unselected population including patients with atrial fibrillation demonstrates that 320-row CT may significantly reduce the radiation dose and amount of contrast agent required compared with ICA while maintaining a very high diagnostic accuracy.

Epileptic motor behaviors during sleep: anatomo-electro-clinical features.

BACKGROUND: Sleep-related complex motor seizures have long been considered pathognomonic features of Nocturnal Frontal Lobe Epilepsy (NFLE). In recent years, these manifestations have also been reported to have a temporal or insular origin. METHOD: We describe 40 drug-resistant epileptic patients with complex motor seizures during sleep, submitted to presurgical stereo-EEG (SEEG) evaluation and seizure-free after surgical resection of the epileptogenic zone. RESULTS: In a significant proportion (30%) of these patients, seizures arose from extra-frontal regions, including mainly the temporal lobe and the insular cortex, but also the parietal and occipital lobes. In patients with extra-frontal epilepsy, when complex motor behaviors appeared, SEEG revealed that the ictal discharge involved the cingulate and the frontal regions. Finally, at histology, Taylor's focal cortical dysplasia (TFCD) was the most common finding (90% of patients), independent of the site of seizure onset. CONCLUSION: As previously reported by other studies, this histologic substrate may be a major determinant of sleep-related seizures in drug-resistant epileptic patients.

Systematic preoperative coronary angiography and stenting improves postoperative results of carotid endarterectomy in patients with asymptomatic coronary artery disease: a randomised controlled trial.

OBJECTIVE: To evaluate the usefulness of systematic coronary angiography followed, if needed, by coronary artery angioplasty (percutaneous coronary intervention (PCI)) on the incidence of cardiac ischaemic events after carotid endarterectomy (CEA) in patients without evidence of coronary artery disease (CAD). MATERIALS AND METHODS: From January 2005 to December 2008, 426 patients, candidates for CEA, with no history of CAD and with normal cardiac ultrasound and electrocardiography (ECG), were randomised into two groups. In group A (n=216) all the patients had coronary angiography performed before CEA. In group B, all the patients had CEA without previous coronary angiography. In group A, 66 patients presenting significant coronary artery lesions at angiography received PCI before CEA. They subsequently underwent surgery under aspirin (100 mg day(-1)) and clopidogrel (75 mg day(-1)). CEA was performed within a median delay of 4 days after PCI (range: 1-8 days). Risk factors, indications for CEA and surgical techniques were comparable in both groups (p>0.05). The primary combined endpoint of the study was the incidence of postoperative myocardial ischaemic events combined with the incidence of complications of coronary angiography. Secondary endpoints were death and stroke rates after CEA and incidence of cervical haematoma. RESULTS: Postoperative mortality was 0% in group A and 0.9% in group B (p=0.24). One postoperative stroke (0.5%) occurred in group A, and two (0.9%) in group B (p=0.62). No postoperative myocardial event was observed in group A, whereas nine ischaemic events were observed in group B, including one fatal myocardial infarction (p=0.01). Binary logistic regression analysis demonstrated that preoperative coronary angiography was the only independent variable that predicted the occurrence of postoperative coronary ischaemia after CEA. The odds ratio for coronary angiography (group A) indicated that when holding all other variables constant, a patient having preoperative coronary angiography before carotid surgery was 4 times less likely to have a cardiac ischaemic event after carotid surgery. No complications related to coronary angiography were observed and no cervical haematomas occurred in patients undergoing surgery under aspirin and clopidogrel in this study. CONCLUSIONS: Systematic preoperative coronary angiography, possibly followed by PCI, significantly reduces the incidence of postoperative myocardial events after CEA in patients without clinical evidence of CAD.

The shape of human atrial action potential accounts for different frequency-related changes in vitro.

We aimed at investigating frequency-related changes of human atrial action potential (AP) in vitro to see whether baseline AP shape might account for different responses to increasing stimulation rates. Human right atrial trabeculae (n = 48) obtained from adult (n = 38, mean age 59 +/- 8, range 45-72 years) consecutive patients (approximately equal to 30% of those operated upon by a single surgeon; 1.26 preparations per patient, range 1-2) were superfused in an organ bath with oxygenated (O2 content 16 ml/l) and modified (NaHCO3 25.7 mmol/l) Tyrode's solution at 31 degrees C. Baseline electrophysiology (pacing: 1 ms duration, 2-4 mA current intensity) at cycle length (CL) of 1000 ms was recorded in 90% (43 out of 48) of the preparations. The frequency-related protocol (CL from 1600 to 300 ms) was, however, undertaken in 23 (48%) preparations because 20 (42%) became pacing unresponsive immediately after baseline recordings. No statistical differences were seen when baseline electrophysiological parameters (mean +/- SD) were grouped according to late pacing responsiveness (n = 43 vs. n = 23): respectively, resting membrane potential (RMP) was -74 +/- 6 vs. -75 +/- 4 mV, maximal upstroke velocity (Vmax) 172 +/- 60 vs. 173 +/- 39 V/s, AP amplitude (APA) 89 +/- 11 vs. 91 +/- 8 mV and AP durations were at 30% (APD30%) 10 +/- 13 vs. 13 +/- 18 ms, 50% (APD50%) 45 +/- 79 vs. 62 +/- 91 ms and 90% (APD90%) 383 +/- 103 vs. 407 +/- 108 ms. To classify baseline AP shape, two criteria were adopted: criterion 1 ("objective"), based on APA (cut-off 90 mV) and APD90% (cut-off 500 ms) computed values and criterion 2 ("visual") derived from the literature. These criteria enabled us to differentiate three AP shape types: type 1 (spike and dome), type 3 (no dome) and type 4 (extremely prolonged). At baseline, the two criteria diagnosed different proportions of AP shape types. There were, however, no intra-type statistical differences among electrophysiological parameters. By criterion 1, analysis of variance (ANOVA) showed significant inter-type differences of RMP,Vmax, APA, APD50 and 90% and by criterion 2 of APA, APD30, 50 and 90%, respectively. To facilitate comparisons with previous published data, criterion 2 was selected to analyse frequency-related changes of AP shape types. At low stimulation rate, ANOVA for repeated measures (with Greenhouse-Geisser epsilon correction) showed inter-type differences for APD30, 50 and 90% (P = 0.00005). RMP, Vmax, APA and APD90% were overall frequency-related (P = 0.00005). Inter-type frequency-related differences were however seen only for APD90%. Human atrial AP durations (30, 50 and 90%) enable differentiation among AP shape types (1, 3 and 4). By a standardized use-dependent protocol overall RMP, Vmax, APA and APD90% are frequency-related. AP shape accounts for frequency-related changes of APD90% only. A type 4 AP shape with much prolonged AP duration had a flat frequency dependence. At high stimulation rates, adult type 1 and 3 AP shapes are indistinguishable. Use-dependent and pharmacological investigations in human atrial myocytes need to take AP shape into account.

Activation or block of adenosine triphosphate-sensitive potassium channel have opposite effects on postcardioplegic myocardial dysfunction, "stunning". A multivariate prediction based on relative operating characteristic curve.

The relative effects of nicotinic acid (NA) and nitroglycerin (NT) added to cold high K+ cardioplegia were studied, to represent the two moieties of the adenosine triphosphate-sensitive potassium channel (KATP) activator nicorandil (N). In addition, we made a pooled analysis of a large series of experiments performed in our Laboratory to investigate the effects of KATP activation by N, or block (by glibenclamide, G), on postcardioplegic myocardial dysfunction. In both studies, reversibility from myocardial dysfunction (stunning) was assessed by the positive inotropic agent dobutamine. Guinea pig papillary muscle preparations were immersed in Tyrode's solution (O2 content 16 ml/l, 37 degrees C), then hypoxic (O2 content 5 ml/l) superfusion with hypothermic (20 degrees C) cardioplegic Saint Thomas' Hospital solution (STHS) was performed for 120 min. We investigated: A) 5 groups based on treatments added to STHS: 1) saline (Control (C)); 2) N = 1 mmol/L; 3) G = 1 mumol/L (also given for 15 min in Tyrode's solution); 4) NA = 1 mmol/L; 5) NT = 100 mumol/L; B) 76 consecutive experiments and we defined, independent of whether just before or during STHS: 1) KATP activation (by N, in the concentration range 1 mumol/L to 1 mmol/L, n = 36); 2) KATP block (by G 1 mumol/L, either alone or just before N, n = 20); 3) controls (n = 20) (either saline, n = 12, or saline plus dimethyl sulfoxide, as vehicle, at the ratio 100 to 1, n = 8). Absolute isometric contractility variables were evaluated along with percent changes of baseline values: 1) at 30 s of STHS, 2) after 60 min of reoxygenation with Tyrode's solution and 3) following further 15 min of dobutamine 10 mumol/L. In all preparations, developed tension (DT), time to peak tension (TPT), DT/TPT and time to arrest (TTA) were measured. In study A): TTA was significantly abbreviated (intergroup F = 5.79, p < 0.001) in N (49 +/- 11 s, mean +/- SD) p < 0.01 vs C and NA). At 30 s of STHS %DT/TPT was unchanged among groups. By contrast, after 60 min of reoxygenation %DT/TPT in N (118 +/- 35%, p < 0.05 vs C, p < 0.01 vs G) was improved (intergroup F = 5.48, p < 0.002). G, NA and NT showed recovery of contractility similar to C. However, after dobutamine the poorest %DT/TPT were seen in G (p < 0.01 vs C, p < 0.05 vs N). In study B): using the multivariate logistic model, with KATP activation, the odds of normal contractile response, respectively at 60 min of reoxygenation (t = 2.81) and after dobutamine (t = 3.22), were 29.8 and 8.86 of controls, whereas TTA (t = -1.59) was inversely related. Moreover, with KATP block the odds after dobutamine was 0.204 of controls. The relative operating characteristic plots showed areas under the curve greater than 0.7, which is evidence for accurate assessment of the predictive rules adopted. This is the first report where a probabilistic approach to cardioplegia-related experiments showed high accuracy in predicting the recovery of post-hypoxic contractile function (stunning). The results indicate that on postcardioplegic stunning: 1) KATP activation by N and KATP block by G (both given prior to or contemporary with hypoxia) have opposite effects; 2) the favorable effects of nicorandil seem unrelated to its nicotinamide or nitrose moieties.

Activation of ATP-dependent K+ channels enhances myocardial protection due to cold high potassium cardioplegia: a force-frequency relationship study.

The hypothesis that nicorandil might enhance myocardial protection due to cold St Thomas' Hospital (STH) solution ([K+]o 16 mmol/l) through opening of cardiac KATP channels was assessed in isometrically contracting guinea-pig papillary muscles submitted to 120 min of cardioplegic hypoxia followed by 60 min of normothermic reoxygenation. Right ventricular papillary muscles were paced (2 ms, 4 mA) in an organ bath and superfused with oxygenated (O2 content 16 ml/l) Tyrode's solution (37 degrees C). The force-frequency relationship in the range 1600-300 ms cycle length (CL) was studied. Preparations were randomized to receive 120 min cold (20 degrees C), non-oxygenated (O2 content 5 ml/l) STH solution while continuously stimulated at 1600 ms CL, with: (1) saline (No-additive, n = 12); (2) DMSO 1% (Vehicle, n = 8); (3) nicorandil 1 mmol/l (n = 8); (4) nicorandil 1 mmol/l plus glibenclamide 1 mumol/l, the latter also given, before STH solution, in Tyrode's solution for 15 min (n = 8); (5) glibenclamide 1 mumol/l, also circulated, before STH solution, in Tyrode's solution for 15 min (n = 8); (6) nitroglycerin 100 mumol/l (n = 4); in addition, we studied: (7) STH solution with no-additive and no-pacing (n = 4); (8) cold Tyrode's in place of cold STH solution (n = 4). Inotropic state was investigated by measuring: (i) velocity of developed tension (DT), obtained by dividing DT by time to peak tension; (ii) percentage (from precardioplegia values) velocity changes of DT; (iii) log velocity of DT. Post-cardioplegic recovery of contractility (including force-frequency relationship) was assessed in all preparations: (a) 60 min after reoxygenation with Tyrode's solution; (b) after further 15 min superfusion with the positive inotropic agent dobutamine (10 mumol/l). In parallel experiments, action potential duration (APD) 50% changes induced by nicorandil or glibenclamide plus nicorandil in spontaneously beating atrial (n = 4) or electrically driven (1600 ms CL) ventricular (n = 8) tissues during 10 min of STH solution were investigated. Based on force-frequency relationship, at 60 min reoxygenation, in absence of cardioplegia, the lowest recovery of myocardial contractility was seen (stunning). In STH solution, there was moderate to severe stunning, which was unaffected by removing pacing during cardioplegia, or by vehicle or nitroglycerin. In contrast, nicorandil improved recovery of contractility (F = 3.01, P = 0.0106). After dobutamine, nicorandil preparations showed the highest positive inotropic response, which was completely offset by glibenclamide (F = 3.47, P = 0.0046).(ABSTRACT TRUNCATED AT 400 WORDS)

The risk of myocardial stunning is decreased concentration-dependently by KATP channel activation with nicorandil before high K+ cardioplegia.

BACKGROUND: Drug-induced opening of the adenosine triphosphate-sensitive potassium channel (KATP) during hypoxia and/or ischemia, achieved significant myocardial protection in several in vitro and in vivo models. Pretreatment with KATP openers simulated preconditioning and thus enhanced recovery from ischemia. We have demonstrated that the risk of hypoxia-induced myocardial stunning is reversed by KATP activation with 1 mmol/l nicorandil before cold cardioplegic arrest. Whether lower concentrations were effective is not known. METHODS: In guinea pig papillary muscle preparations contracting isometrically (driven at 1600 ms cycle), nicorandil was superfused (15 min) either 1 mumol/l (n = 4), 30 mumol/l (n = 4), 100 mumol/l (n = 4), or 1 mmol/l (n = 8) in Tyrode's solution (oxygen content 16 ml/l, 37 degrees C, 5 ml/min). Controls were superfused with saline (Tyrode's solution: n = 8). A group containing vehicle (DMSO 1%, n = 8) was also studied. In four preparations the KATP channel blocker glibenclamide 1 mumol/l was given before nicorandil 1 mmol/l. Then, long-lasting (120 min) but moderately hypoxic (oxygen content 5 ml/l: 31% of Tyrode's solution) superfusion with hypothermic (20 degrees C) high K+ (16 mmol/l) cardioplegic solution (5 ml/min) was performed. Recovery of contractility was evaluated after further 60 min of reoxygenation with Tyrode's solution based on DT/TPT (developed tension divided by time to peak tension) as percent of prehypoxia basal values (%DT/TPT60). DT/TPT was also studied following 15 min of inotropic stimulation with dobutamine 10 mumol/l (%DT/TPT75). To assess the risk of stunning, we used a multivariate linear model by all possible subsets analysis (BMDP-9R) aimed at predicting both %DT/TPT60 and %DT/TPT75 (as continuous dependent variables). RESULTS: During cardioplegia induction, time to arrest (TTA) was (mean +/- S.D.) 103 +/- 48s in control preparations which had poor recovery of contractility (stunning) after reoxygenation (%DT/TPT60: 71 +/- 20%; %DT/TPT75: 443 +/- 272%). Nicorandil (1 mumol/l-1 mmol/l) abbreviated TTA concentration-dependently (163 +/- 74, 149 +/- 103, 82 +/- 20, and 56 +/- 27s) and improved both %DT/TPT60 (63 +/- 9, 78 +/- 17, 87 +/- 13, and 98 +/- 11%) and %DT/TPT75 (587 +/- 333, 619 +/- 107, 971 +/- 301, and 666 +/- 400%). Glibenclamide reversed the effects of nicorandil 1 mmol/l (TTA: 165 +/- 30 s, P < 0.01; %DT/TPT60: 43 +/- 12, P < 0.01; %DT/TPT75: 272 +/- 147, P < 0.05). Multivariate prediction of myocardial stunning at both 60 and 75 min reoxygenation showed that nicorandil (30 mumol/l-1 mmol/l) was a significant (P < 0.001) protectant whereas glibenclamide was a significant risk factor (P = 0.009). It is unclear whether negative inotropic effects of nicorandil (%DT/TPT at the end of pretreatment) was mechanistically related to reduced risk of stunning since contribution was seen only to predict %DT/TPT75 (t = 3.24, P = 0.003) whereas a positive association was observed with %DT/TPT60 (t = 1.89, P = 0.068). CONCLUSION: Pretreatment with nicorandil concentration-dependently enhanced the cardioprotective effect of hypothermic high K+ cardioplegia. The risk of myocardial stunning was decreased by KATP opening with nicorandil and increased by KATP block with glibenclamide. Inotropic stimulation with dobutamine might unravel the role of negative inotropic effect of KATP opening as a contributory factor to explain the efficacy of nicorandil in our model.

Pretreatment with the adenosine triphosphate-sensitive potassium channel opener nicorandil and improved myocardial protection during high-potassium cardioplegic hypoxia.

We hypothesized that pretreatment with the potassium channel opener nicorandil might enhance myocardial protection achieved by cold (20 degrees C) high-potassium (16 mmol/L) cardioplegia (5 ml/min) during long-duration (120 minutes) myocardial hypoxia (average oxygen content 5.4 ml/dl). We tested a 15-minute infusion of nicorandil (1 mmol/L) given only before (group A, n = 8) or before and during cardioplegia (group B, n = 8) in guinea pig papillary muscle preparations contracting isometrically while stimulated (4 mA, 2 msec) at 1600 msec cycle length. Nicorandil was significantly negative inotropic before cardioplegia and shortened significantly action potential duration. During cardioplegia, time to arrest of contraction was shortened from 145 +/- 28 seconds (mean +/- standard error) in the vehicle group (dimethyl sulfoxide 1:100; n = 8) to 56 +/- 10 seconds (p < 0.02) and 68 +/- 5 seconds (p < 0.05) in groups A and B, respectively. Recovery of developed tension at 60 minutes of normothermic reoxygenation (expressed as percent of prehypoxia basal value) was ameliorated from 54% +/- 6% (vehicle group) to 92% +/- 4% (group A, p < 0.01) and to 119% +/- 19% (group B, p < 0.01). The specific potassium channel blocker glibenclamide (glib: 1 mumol/L, n = 8) prolonged action potential duration and was without effect on time to arrest. On reoxygenation, the glib group had prolonged time to half relaxation (versus group A, p < 0.02) and the worst percent developed tension at 60 minutes (40% +/- 4%). In the overall study, time to arrest and percent developed tension at 60 minutes were inversely correlated (r = -0.45, p < 0.01). Arrhythmias were never observed. Multivariate analysis showed that pretreatment with nicorandil (with or without drug adjunct to cardioplegic solution) was a significant factor (r2 = 0.65, p = 0.0001) to influence reoxygenation-mediated recovery of mechanical function. Neither the negative inotropic effect of nicorandil before cardioplegia nor its abbreviating action on time to arrest during cardioplegia was contributory to explain recovery of function on reoxygenation. In subgroup analysis, negative inotropism and the shortening of action potential duration were contributory factors. These data suggest that nicorandil pretreatment activates potassium channels and enhances the myocardial protection provided by cold cardioplegia an effect, which is evident after a long hypoxic period, late on reoxygenation.

Multivariate prediction of spontaneous repetitive responses in ventricular myocardium exposed in vitro to simulated ischemic conditions.

Guinea-pig ventricular myocardium was partly exposed to normal Tyrode's superfusion and partly to altered conditions (using modified Tyrode's solution) set to simulate acute myocardial ischemia (PO2 80 +/- 10 mmHg; no glucose; pH 7.00 +/- 0.05; K+ 12 mM). Using a double-chamber tissue bath and standard microelectrode technique, the occurrence of spontaneous repetitive responses was investigated during simulated ischemia (occlusion) and after reperfusing the previously ischemic superfused tissue with normal Tyrode's solution (reperfusion). In 62 experiments (42 animals) the effects of: (1) duration of simulated ischemia (1321 +/- 435 s), (2) stimulation rate (1002 +/- 549 ms) and (3) number of successive simulated ischemic periods (occlusions) (1.58 +/- 0.92) on: (1) resting membrane potential, (2) action potential amplitude, (3) duration of 50 and 90% action potentials and (4) maximal upstroke velocity of action potential were studied. All variables were considered as gradients (delta) between normal and ischemic tissue. Both during occlusion and upon reperfusion, spontaneous repetitive responses were coded as single, couplets, salvos (three to nine and > 10) or total spontaneous repetitive responses (coded present when at least one of the above-mentioned types was seen). The incidence of total spontaneous repetitive responses was 31% (19/62) on occlusion and 85% (53/62) upon reperfusion. Cox's models (forced and stepwise) were used to predict multivariately the occurrence of arrhythmic events considered as both total spontaneous repetitive responses and as separate entities. These models were applicable since continuous monitoring of the experiments enabled exact timing of spontaneous repetitive response onset during both occlusion and reperfusion. In predicting reperfusion spontaneous repetitive responses, total spontaneous repetitive responses and blocks observed during the occlusion period were also considered. Total occlusion spontaneous repetitive responses were predicted by: (1) longer delta 50% action potential duration (t = 2.68), (2) shorter delta 90% action potential duration (t = -2.17) and (3) fewer occlusive periods (t = -2.46). Total reperfusion spontaneous repetitive responses were predicted by a longer delta action potential amplitude (t = 2.18). Due to few events during occlusion, prediction of individual arrhythmic entities was not possible. Upon reperfusion single spontaneous repetitive responses were predicted by longer delta maximal upstroke velocity of action potential (t = 2.59) and shorter delta 90% action potential duration (t = -2.55); couplets were predicted by longer delta 50% action potential duration (t = 3.26); longer delta action potential amplitude predicted salvos (> 10) (t = 3.26).(ABSTRACT TRUNCATED AT 400 WORDS)

[The inotropic and bathmotropic effects of beta stimulation: a study comparing dobutamine and dopamine on the guinea-pig papillary muscle in isotonic contraction]. / Effetti inotropi e batmotropi della betastimolazione: studio di confronto tra dobutamina e dopamina nel muscolo papillare di cavia in contrazione isotonica.

The study was aimed at comparing the effects of dobutamine (dob) and dopamine (dop) on isotonic contraction and rhythmicity of isolated guinea-pig papillary muscles (in oxygenated Tyrode at 37 degrees C), by taking into account: 1) the rate of stimulation (50% above the diastolic threshold) at 5 fixed periods: (RR: 1600, 1200, 1000, 800 and 400 ms); 2) 7 log concentrations (logC) of the index amine (from 10(-9) to 10(-3) M). To this end, a dose-relation protocol which explored the effects of all 5 RR and 7 logC was designed and 15 adult female Guinea-pigs (250 to 350 g) were randomized to either the dob (n = 8) or the dop (n = 7) arm. This enabled a total of 525 sets of data to be analyzed: in 38 sets (7.2%) premature contractions (CP) were coded. CP were sustained (freq: > 3) in 25 of these latter 38 sets (4.8%). Compared to the basal state, the amplitude (AMP%) and the log of percent amplitude (logAMP%) and time to peak (TP%) changes of the isotonic (Gould transducer) twitch were calculated along with the log of this latter variable (logTP%). AMP%, log AMP%, TP% and logTP% were linearly correlated with logC at all RR. In the range 1600-400 RR, for both amines, significant linear correlations (magnitude of 0.15 > r < magnitude of 0.70, 0.001 > p < 0.022) were seen for plots of AMP%, logAMP% and TP%:steeper correlations were observed for dop. This was confirmed in multivariate analysis (BMDP-9R) whereby AMP%, logAMP%, TP%, logTP%, CP, and freqCP were dependent variables and coded variables were included to either define the type of treatment (dop versus dob) or logC. In these analyses, logC (t > 11) and dop (t > magnitude of 3) might be used to explain (0.28 > r2 < 0.42, 0.00001 > p < 0.0025) AMP% and logAMP%, meaning that a different inotropic (isotonic) efficacy exists between these 2 amines, at all logC. On the other hand, when CP and freqCP were coded, explanatory variables were AMP% and logAMP% (4.86 > t < 6.95, 0.06 > r2 < 0.09, p < 0.00001), but not the variable used to code the type of treatment (dob versus dop).(ABSTRACT TRUNCATED AT 400 WORDS)

[Increase of potassium conductance and spontaneous electric activity in vitro: comparison of nicorandil and cicletanine]. / Aumento della conduttanza al potassio ed attività elettrica spontanea in vitro: confronto tra nicorandil e cicletanine.

Nicorandil (N) increases potassium conductance in vascular smooth muscle and so induces vasodilation; N also dose-dependently reduces action potential duration (APD). However, it is unclear whether increased potassium conductance, and concomitant APD shortening, might be arrhythmogenic, particularly when myocardial ischemia (where potassium efflux is increased) concurs. Data on the anti-arrhythmic effectiveness of N have also been published: N reduced the spontaneous discharge of sino-atrial node and so reduced heart rate, both in vitro and man. On the other hand, among other vasodilators, cicletanine (C) has been reported to increase potassium conductance, an effect which was advocated to explain its antiarrhythmic potency. In the present investigation the direct myocardial effects of N were compared to those following C in 63 experiments (from 13 Guinea-pigs), using atrial strips (containing sino-atrial node) superfused in 1-compartment bath with normal Tyrode's solution. Using glass microelectrodes, standard electrophysiologic variables were recorded (APA, RMP, APD50%, Vmax) in spontaneously beating atrial tissue, either in Tyrode, dimethyl-sulfoxide (DMSO 1:100, as solvent), C 10(-5) M (in DMSO 1:100), and N 10(-3) M (in DMSO 1:100), whose respective perfusion periods (15 min) were randomized, always following 15 min of washout with Tyrode. Only N was tested in experiments of both 15 and 30 min duration.(ABSTRACT TRUNCATED AT 250 WORDS)

ST/HR slope and improved exercise ECG detection of myocardial ischemia in patients with suspected coronary artery disease.

Predictive values of ST/HR slope and ST-segment displacement during symptom-limited exercise were determined in 85 patients who underwent coronary angiography for suspected coronary artery disease, using perfusional and functional radionuclide images with 99mTc-2-methoxy-isobutil-isonitrile as an index of stress-induced myocardial ischemia. ST/HR slope showed a better sensitivity than conventional stress-induced changes of ST-segment displacement (96% vs. 73%, respectively). In patients with clinical suspicion of coronary artery disease, the main result was the negative predictive value of ST/HR slope when compared with conventional ST-segment displacement (98% vs. 41%). ST/HR slope was unable to perfectly separate patients with different degrees of ischemia, however, subjects without scintigraphic signs of stress-induced ischemia and patients with ischemic impairment in three myocardial regions were correctly identified as distinct populations. In patients with a previous myocardial infarction, no difference was found between the two criteria and a wide overlap of ST/HR slope values was present. The authors conclude that ST/HR slope is useful to detect the rate of change in electric parameters during exercise and might therefore more adequately be used to separate normal from definitely abnormal responses to exercise.

[The prevention of an excitation-conduction block during acute myocardial ischemia: is there a role for prostacyclin or for histamine?]. / Prevenzione del blocco dell'eccitoconduzione durante ischemia miocardia acuta: esiste un ruolo per la prostaciclina o per l'istamina?

We have investigated (multivariate Cox's model) the relative risk of stable excitation-conduction block (ECB) in right ventricular myocardial strips (2 x 5 x 1 mm) from 26 female guinea-pigs, bathed in a 2-compartment chamber (3 ml) on the anterior side of which modified Tyrode's solution (K+ 12 mM, HCO3- 9 mM, pH 7 +/- 0.05, pO2 80 +/- 10 mmHg and absence of glucose) is supraperfused (stimulation rate: 450 ms; wire in the posterior compartment), thus enabling simulation of electrophysiologic changes seen during acute myocardial ischemia. Using glass microelectrodes, action potential amplitude (APA), durations (APD50 and 90%), resting membrane potential (RMP) and upstroke velocity (Vmax) are investigated. The hypothesis was tested of prostacyclin and histamine involvement in the genesis of ischemia-induced ECB in this model. Either a weak prostacyclin stimulator (cicletanine 10(-5) M, IPSEN, Paris, F, in DMSO 1:100; n = 16) or a potent prostacyclin generation blocker (indomethacin 10(-5) M, Sigma, in DMSO 1:100; n = 10) and either DMSO alone (1:100; n = 16) or a specific histaminergic H1 receptor antagonist (terfenadine 10(-5) M, Sigma, in DMSO 1:100; n = 10) were supraperfused using a randomization scheme. Each animal was used twice and either a first or a second occlusion (supraperfusing the modified Tyrode's solution for 30 min) period was performed and the randomized substances were supraperfused, thus enabling obtention of n = 52 experiments for analysis.(ABSTRACT TRUNCATED AT 250 WORDS)

Exponential fit of QT interval-heart rate relation during exercise used to diagnose stress-induced myocardial ischemia.

The aim of this study was to analyze the dynamic changes of QT interval--heart rate relation during exercise, fitting their reciprocal variations to an exponential formula (QT = A - B.exp(-k.RR], in order to see whether diagnostic contributions might so be derived. The authors studied 139 patients who underwent a simultaneous assessment of regional myocardial perfusion and ventricular function by means of two injections of 99mTc-methoxy-isobutyl-isonitrile at rest and at peak of a submaximal exercise test, using first pass radionuclide angiography with multielement gamma-camera and single photon emission computerized tomography, in order to detect and localize the presence of stress-induced myocardial ischemia. According to radionuclide results, patients were divided into three groups: group A, 7 individuals with no sign of stress-induced myocardial ischemia; group B, 79 patients with evidence of ischemia in 1 (16.5%), 2 (65.5%), or 3 (17.7%) main coronary territories; and group C, 53 patients with previous infarction and evidence of ischemia in other territories. Conventional analysis of the exercise test (greater than or equal to 0.1 mV ST depression) showed a pathological response in no individual of group A, in 34 patients of group B (43%), and in 27 patients of group C (50.9%); overall sensitivity was 46.2%, specificity 100%, and diagnostic accuracy 48.9%. Exponential coefficients A, B, and k showed wide overlap of values among the three groups, although a significant difference was present in mean k values between groups A and B (p less than 0.001), and group C (p less than 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)