Autonomic blockade during sinusoidal baroreflex activation proves sympathetic modulation of cerebral blood flow velocity.

BACKGROUND AND PURPOSE: Pharmacological blockade showed sympathetic origin of 0.03 to 0.15 Hz blood pressure (BP) oscillations and parasympathetic origin of 0.15 to 0.5 Hz RR-interval (RRI) oscillations, but has not been used to determine origin of cerebral blood flow velocity (CBFV) oscillations at these frequencies. This study evaluated by pharmacological blockade whether 0.1 Hz CBFV oscillations are related to sympathetic and 0.2 Hz CBFV oscillations to parasympathetic modulation. METHODS: In 11 volunteers (24.6 ± 2.3 years), we monitored RRIs, BP, and proximal middle cerebral artery CBFV, at rest, during 180 s sympathetic BP activation by 0.1 Hz sinusoidal neck suction (NS), and during 180 s parasympathetic RRI activation by 0.2 Hz NS. We repeated recordings after 25 mg carvedilol, and after 0.04 mg/kg atropine. Autoregressive analysis quantified RRI-, BP-, and CBFV-spectral powers at 0.1 Hz and 0.2 Hz. We compared parameters at rest, during 0.1 Hz, or 0.2 Hz NS, with and without carvedilol or atropine (analysis of variance, post hoc testing; significance, P<0.05). RESULTS: Carvedilol significantly increased RRIs and lowered BP, CBFV, and 0.1 Hz RRI-, BP-, and CBFV-powers at baseline (P=0.041 for CBFV-powers), and during 0.1 Hz NS-induced sympathetic activation (P<0.05). At baseline and during 0.2 Hz NS-induced parasympathetic activation, atropine lowered RRIs and 0.2 Hz RRI-powers, but did not change BP, CBFV, and 0.2 Hz BP- and CBFV-powers. CONCLUSIONS: Attenuation of both 0.1 Hz CBFV and BP oscillations after carvedilol indicates a direct relation between 0.1 Hz CBFV oscillations and sympathetic modulation. Absent effects of atropine on BP, CBFV, and 0.2 Hz BP and CBFV oscillations suggest that there is no direct parasympathetic influence on 0.2 Hz BP and CBFV modulation.

Engineered heart tissue grafts improve systolic and diastolic function in infarcted rat hearts.

The concept of regenerating diseased myocardium by implantation of tissue-engineered heart muscle is intriguing, but convincing evidence is lacking that heart tissues can be generated at a size and with contractile properties that would lend considerable support to failing hearts. Here we created large (thickness/diameter, 1-4 mm/15 mm), force-generating engineered heart tissue from neonatal rat heart cells. Engineered heart tissue formed thick cardiac muscle layers when implanted on myocardial infarcts in immune-suppressed rats. When evaluated 28 d later, engineered heart tissue showed undelayed electrical coupling to the native myocardium without evidence of arrhythmia induction. Moreover, engineered heart tissue prevented further dilation, induced systolic wall thickening of infarcted myocardial segments and improved fractional area shortening of infarcted hearts compared to controls (sham operation and noncontractile constructs). Thus, our study provides evidence that large contractile cardiac tissue grafts can be constructed in vitro, can survive after implantation and can support contractile function of infarcted hearts.

Atorvastatin enhances interleukin-10 levels and improves cardiac function in rats after acute myocardial infarction.

LV (left ventricular) remodelling is the basic mechanism of HF (heart failure) following MI (myocardial infarction). Although there is evidence that pro-inflammatory cytokines [including TNF-alpha (tumour necrosis factor-alpha) and IL-6 (interleukin-6)] are involved in the remodelling process, only little is known about the role of anti-inflammatory cytokines, such as IL-10. As accumulating evidence has revealed that statins possess anti-inflammatory properties, the aim of the present study was to elucidate the effect of atorvastatin on the modulation of the anti-inflammatory cytokine IL-10 and its effect on LV function in rats with HF subsequent to MI. Rats with MI, induced by permanent LAD (left anterior descending) branch coronary artery ligation, were treated for 4 weeks with atorvastatin (10 mg x kg(-1) of body weight x day(-1) via oral gavage) starting on the first day after induction of MI. Cardiac function was assessed by echocardiography and cardiac catheterization 4 weeks after MI induction. Membrane-bound and soluble fractions of TNF-alpha, IL-6 and IL-10 protein, the TNF-alpha/IL-10 ratio, serum levels of MCP-1 (monocyte chemoattractant protein-1) as well as myocardial macrophage infiltration were analysed. Treatment with atorvastatin significantly improved post-MI LV function (fractional shortening, +120%; dP/dt(max), +147%; and LV end-diastolic pressure, -27%). Furthermore atorvastatin treatment markedly decreased the levels of TNF-alpha, IL-6 and MCP-1, reduced myocardial infiltration of macrophages and significantly increased myocardial and serum levels of the anti-inflammatory cytokine IL-10. Thus the balance between pro-inflammatory and anti-inflammatory cytokines was shifted in the anti-inflammatory direction, as shown by a significantly decreased TNF-alpha/IL-10 ratio. Atorvastatin ameliorated early LV remodelling and improved LV function in rats with HF subsequent to MI. Our study suggests that the modulation of the balance between pro- and anti-inflammatory cytokines towards the anti-inflammatory cytokine IL-10 is one salutary mechanism underlying how atorvastatin influences post-MI remodelling and thus improves LV function.

Interleukin-10 improves left ventricular function in rats with heart failure subsequent to myocardial infarction.

Evidence has shown that pro-inflammatory cytokines, especially TNF-alpha, are involved in the inflammatory response in the remodelling process after myocardial infarction (MI). Although IL-10, an anti-inflammatory cytokine, has been shown to antagonize some of the deleterious effects of TNF-alpha, little is known about its role in post-MI left ventricular (LV) dysfunction. The aim of the present study was to investigate whether a therapy with rhIL-10 could be beneficial in an animal model of post-MI heart failure (HF). Rats with experimental MI were treated with rhIL-10 (75 microg/kg/d sc) starting directly after MI induction, and continuing for 4 weeks. Controls were untreated MI and sham-operated rats. Cardiac function was assessed by echocardiography and cardiac catheterization 4 weeks after MI induction. Membrane-bound and soluble fractions of TNF-alpha, IL-6 and IL-10, the ratio of TNF-alpha to IL-10, serum levels of MCP-1 as well as myocardial macrophage infiltration, were analyzed. Treatment with rhIL-10 significantly improved post-MI LV function (FS +127%;, dP/dt(max) +131%; LVEDP -36%). This effect was associated with a significant decrease in pro-inflammatory cytokine and chemokine levels (TNF-alpha, IL-6, MCP-1) and furthermore resulted in a reduced myocardial infiltration of macrophages.

Real-time myocardial contrast echocardiography for assessing perfusion and function in healthy and infarcted wistar rats.

Real-time myocardial contrast echocardiography (MCE) is a noninvasive perfusion imaging method, whereas technical and resolution problems impair its application in small animals. Hence, we investigated the feasibility of MCE in experimental cardiovascular set-ups involving healthy and infarcted myocardium in rats. Twenty-five male Wistar rats were examined under volatile anesthesia (2.5% isoflurane) with high-resolution conventional 2-D echocardiography (2DE) and real-time MCE (Sonos 7,500 with 15MHz-transducer, Philips Medical Systems, Andover, MA, USA) in short-axis view. Contrast agent (SonoVue, Bracco, Milan, Italy) was infused as a bolus into a sublingual vein. Background-subtracted contrast signal intensity (SI) was measured off-line in six end-systolic segments and fitted to an exponential curve (gamma variate). Derived peak SI was subsequently calculated and compared with wall motion and common functional measured quantities (left ventricular end-diastolic diameter [LVEDD], area shortening [AS]). Recordings were performed before and 14 days after left anterior descending (LAD) ligature. Infarction induced anterior wall motion abnormalities (WMA) in all animals (16 akinetic, 9 hypokinetic), increased LVEDD (9.1 +/- 0.6 vs. 7.9 +/- 0.6 mm, p < 0.001), reduced AS (36.1 +/- 10.0 vs. 59.5 +/- 4.1%, p < 0.001) and reduced anterior segmental SI (0.4 +/- 0.4 dB akinetic / 1.7 +/- 1.7 dB hypokinetic vs. 15.8 +/- 10.9 dB preinfarct, p < 0.001 / p < 0.001). Segmental SI in normokinetic segments remained unchanged. Area at risk (perfusion defect) correlated well with WMA (r = 0.838). These data confirmed high-resolution real-time MCE as a rational tool for assessing myocardial perfusion of Wistar rats. It may therefore be a useful diagnostic tool for in-vivo cardiovascular research in small animals.

Reproducibility of transthoracic echocardiography in small animals using clinical equipment.

OBJECTIVE: Transthoracic echocardiography has been employed to assess left ventricular dimensions and function in small animals. The aim of this study was to identify the limits of transthoracic echocardiography in a commonly used Wistar rat model by assessing intraobserver variability, interobserver variability, and day-to-day variability of examinations implying registrations and measurements. METHODS: Twenty male adult Wistar rats (body weight 496+/-52 g) were examined under volatile isoflurane anesthesia (heart rate 302+/-26 bpm) by transthoracic echocardiography (Sonos 7500; Philips) with a 15 MHz-transducer. For calculation of intraobserver variability, examinations were repeated by the same examiner and for interobserver variability, examinations were performed independently by two investigators. For day-to-day variability, examinations were repeated 14 days later. Left ventricular diameters and areas were analyzed in parasternal short axis and in a modified parasternal long axis. Fractional shortening, area shortening, ejection fraction, stroke volume, and cardiac output were calculated. RESULTS: Left ventricular end-diastolic diameter was 8.9+/-0.6 mm, fractional shortening 39.0+/-5.3%, area shortening 59.6+/-6.1%, ejection fraction 83.3+/-5.1%, stroke volume 0.24+/-0.06 ml, and cardiac output 72.9+/-20.6 ml/min. Intraobserver variability of left ventricular end-diastolic diameter, fractional shortening, area shortening, and ejection fraction was less than 10%, increasing to 19% for stroke volume and cardiac output. Interobserver variability of left ventricular end-diastolic diameter, fractional shortening, area shortening, ejection fraction was less than 13%, increasing to 23% for stroke volume and 25% for cardiac output. Day-to-day variability of left ventricular end-diastolic diameter, area shortening, ejection fraction was less than 11% whereas for stroke volume it was 21% and for cardiac output it was 22%. F-ratio test comparing investigated variabilities did not reveal significant differences. CONCLUSIONS: M-mode and two-dimensional echocardiography in large rats by clinically common high-end ultrasound systems can be assessed reliably. Parameters of global left ventricular performance like stroke volume and cardiac output could not be assessed with similar reliability.

Patent foramen ovale as lifesaving purging valve.

Patent foramen ovale is considered as a potential risk factor for stroke owing to paradoxic embolism, leading to the question "to close or not to close the patent foramen ovale". We report a 26-year-old woman with chest pain, dyspnoea, sudden severe pain in both legs and paraplegia. Thoracic and abdominal computed tomography revealed massive pulmonary embolism and complete obstruction of the abdominal aorta. Interventional removal of the aortic thrombus was undertaken using the Fogarty catheter technique via the femoral arterial approach. As a result of worsening of cardiopulmonary function during the procedure, additional local thrombolysis, with a total of 50 mg recombinant tissue plasminogen activator, and fragmentation of the thrombus in the right pulmonary artery were performed via a femoral vein approach. Ultrasound studies revealed a patent foramen ovale of about 12 mm diameter with a significant right to left shunt. Under favourable conditions, a patent foramen ovale may allow the escape of a thrombus, sufficient to cause a potentially fatal pulmonary embolism, into the arterial system, where it can be removed by interventional manoeuvres.

Partial pharmacologic blockade shows sympathetic connection between blood pressure and cerebral blood flow velocity fluctuations.

Cerebral autoregulation (CA) dampens transfer of blood pressure (BP)-fluctuations onto cerebral blood flow velocity (CBFV). Thus, CBFV-oscillations precede BP-oscillations. The phase angle (PA) between sympathetically mediated low-frequency (LF: 0.03-0.15Hz) BP- and CBFV-oscillations is a measure of CA quality. To evaluate whether PA depends on sympathetic modulation, we assessed PA-changes upon sympathetic stimulation with and without pharmacologic sympathetic blockade. In 10 healthy, young men, we monitored mean BP and CBFV before and during 120-second cold pressor stimulation (CPS) of one foot (0°C ice-water). We calculated mean values, standard deviations and sympathetic LF-powers of all signals, and PAs between LF-BP- and LF-CBFV-oscillations. We repeated measurements after ingestion of the adrenoceptor-blocker carvedilol (25mg). We compared parameters before and during CPS, without and after carvedilol (analysis of variance, post-hoc t-tests, significance: p<0.05). Without carvedilol, CPS increased BP, CBFV, BP-LF- and CBFV-LF-powers, and shortened PA. Carvedilol decreased resting BP, CBFV, BP-LF- and CBFV-LF-powers, while PAs remained unchanged. During CPS, BPs, CBFVs, BP-LF- and CBFV-LF-powers were lower, while PAs were longer with than without carvedilol. With carvedilol, CPS no longer shortened resting PA. Sympathetic activation shortens PA. Partial adrenoceptor blockade abolishes this PA-shortening. Thus, PA-measurements provide a subtle marker of sympathetic influences on CA and might refine CA evaluation.

Cardiac grafting of engineered heart tissue in syngenic rats.

BACKGROUND: Cell grafting has emerged as a novel approach to treat heart diseases refractory to conventional therapy. We hypothesize that survival and functional and electrical integration of grafts may be improved by engineering cardiac tissue constructs in vitro before grafting. METHODS AND RESULTS: Engineered heart tissue (EHT) was reconstituted by mixing cardiac myocytes from neonatal Fischer 344 rats with liquid collagen type I, matrigel, and serum-containing culture medium. EHTs were designed in circular shape (inner/outer diameter: 8/10 mm; thickness: 1 mm) to fit around the circumference of hearts from syngenic rats. After 12 days in culture and before implantation on uninjured hearts, contractile function of EHT was measured under isometric conditions. Baseline twitch tension amounted to 0.34+/-0.03 mN (n=33) and was stimulated by Ca(2+) and isoprenaline to 200+/-12 and 185+/-10% of baseline values, respectively. Despite utilization of a syngenic model immunosuppression (mg/kg BW: azathioprine 2, cyclosporine A 5, methylprednisolone 2) was necessary for EHT survival in vivo. Echocardiography conducted 7, 14, and 28 days after implantation demonstrated no change in left ventricular function compared with pre-OP values (n=9). Fourteen days after implantation, EHTs were heavily vascularized and retained a well organized heart muscle structure as indicated by immunolabeling of actinin, connexin 43, and cadherins. Ultrastructural analysis demonstrated that implanted EHTs surpassed the degree of differentiation reached before implantation. Contractile function of EHT grafts was preserved in vivo. CONCLUSIONS: EHTs can be employed for tissue grafting approaches and might serve as graft material to repair diseased myocardium.

Acromegaly per se does not increase the risk for coronary artery disease.

CONTEXT: Information about the risk and course of coronary artery disease (CAD) in acromegaly is limited. OBJECTIVE: To evaluate CAD risk in acromegalic patients at diagnosis and after successful treatment during follow-up. SUBJECTS AND METHODS: Twenty-five consecutive patients (age 45.1+/-10.6 years, 15 women) were studied at the time of diagnosis, and 19 patients were re-evaluated after 4.6+/-1.1 years. The European Society of Cardiology (ESC) risk score was calculated, and a cardiac computed tomography was performed for detection and quantification (Agatston score (AS)) of coronary artery calcium (CACs). Fifty age-, sex-, and CAD risk-matched subjects and CAC data from the population-based Heinz Nixdorf Recall (HNR) study served as controls. RESULTS: In 21 of the 25 patients, the 10-year risk of developing CAD according to the ESC risk score was low (<10%) and high (>20%) in four patients. The AS was lower than in controls (2.6+/-7.9 vs 66+/-182; P=0.014) and less patients had a positive CAC (AS>0) (20 vs 48%, P=0.024), which in the acromegalic patients was less than expected from the HNR study. The AS did not correlate with GH excess or disease duration. In 19 acromegalic patients, who were in remission and re-evaluated after 4.6+/-1.1 years, the ESC risk (P=0.102) and the AS (P=0.173) did not change significantly and no symptomatic CAD event occurred. CONCLUSION: CAD risk in newly diagnosed acromegalic patients was low and remained stable after successful treatment. CAC was lower than in controls suggesting that GH excess per se does not carry an additional CAD risk.

Real-time myocardial contrast stress echocardiography using bolus application.

In myocardial contrast echocardiography (MCE), power modulation technique may quantify myocardial perfusion in real-time. However, constant infusion of the contrast agent (CA) complicates handling. This pilot study sought for the clinical feasibility of quantitative MCE by a CA bolus application during Adenosine stress echocardiography to diagnose coronary artery disease (CAD). Twenty-four consecutive patients (pts) with contemporary coronary angiography underwent rest and maximum Adenosine stress. Signal intensity could be calculated in 316/348 left ventricular (LV) segments (91%) (18-segment model). At rest, gamma-variate (alpha) as well as saturation function (beta) was not significantly different in healthy men (n = 268) as well as CAD pts (n = 48) (alpha: 0.34 s(-1) versus 0.40 s(-1), n.s.; beta: 0.31 s(-1) versus 0.35 s(-1), n.s.). During Adenosine infusion both values increased in healthy men (alpha: 0.34 +/- 0.37 s(-1) versus 0.44 +/- 0.45 s(-1), p < 0.05; beta: 0.31 +/- 0.33 s(-1) versus 0.40 +/- 0.40 s(-1), p < 0.01), but not in CAD (alpha: 0.40 +/- 0.35 s(-1) versus 0.29 +/- 0.29 s(-1), n.s.; beta: 0.35 +/- 0.32 s(-1) versus 0.27 +/- 0.30 s(-1), n.s.). Sensitivity of alpha/beta reserve

Cardiac amyloidosis imaged by dual-source computed tomography.

The ability of contrast-enhanced CT to detect "late enhancement" in a fashion similar to magnetic resonance imaging has been reported previously. Typical myocardial distribution patterns of "late enhancement" have been described for MRI. The same patterns can be observed in CT imaging, albeit at a lower signal to noise ratio. We report a case of cardiac amyloidosis with a typical pattern of subendocardial, circumferential late enhancement in all four cardiac chambers.