Left ventricular systolic/diastolic function evaluated by quantitative ECG-gated SPECT: comparison with echocardiography and plasma BNP analysis.

OBJECTIVE: The aim of this study was to evaluate the left ventricular (LV) functional parameters calculated using quantitative electrocardiography (ECG)-gated myocardial perfusion single photon emission computed tomography (QGS). In addition to LV systolic parameters, diastolic parameters were compared with those by ultrasound echocardiography (UCG) and also with plasma B-type natriuretic peptide (BNP) concentrations. METHODS: We examined 46 patients with various forms of heart disease. By the QGS data with 16 framing data acquisition using technetium (Tc)-99m methoxyisobutylisonitrile (MIBI) perfusion, we calculated the following parameters: LV end-diastolic volume (EDV), end-systolic volume (ESV), ejection fraction (EF), peak filling rate (PFR), filling rate during the first third of the filling time (1/3FR) and first third filling fraction (1/3FF). By UCG, we measured mitral early to atrial (E/A) wave velocity ratio and pulmonary venous inflow systolic/diastolic (S/D) ratio as diastolic functional parameters. Plasma BNP concentrations were also measured. RESULTS: There was a significant correlation between LVEDV, ESV and EF measured by QGS and UCG (EDV, r = 0.71, p < 0.001; ESV, r = 0.82, p < 0.001; EF, r = 0.75, p < 0.001). The PFR, 1/3FR and 1/3FF obtained by QGS correlated positively with E/A ratio (PFR, r = 0.54, p < 0.001; 1/3FR, r = 0.61, p < 0.001; 1/3FF, r = 0.42, p < 0.01) and negatively with S/D ratio (PFR, r = -0.40, p < 0.01; 1/3FR, r = -0.38, p < 0.05; 1/3FF, r = -0.39, p < 0.01) obtained by UCG. Plasma BNP concentrations in EF < 50% patients were greater than those in EF > or = 50% patients (335.2 +/- 60.2 vs. 101.2 +/- 41.3 pg/ml, p < 0.01, both n = 17). Plasma BNP levels were also compared between higher and lower 1/3FF patients matched for LVEF. Plasma BNP concentrations in 1/3FF < 35% patients were significantly greater than those in 1/3FF > or = 35% patients (312.9 +/- 62.5 vs. 120.5 +/- 32.8 pg/ml, p < 0.05, both n = 14). CONCLUSIONS: The degree of LV systolic and diastolic dysfunctions evaluated by QGS correlated with that by UCG or BNP. The QGS functional parameters offer useful information regarding cardiac failure.

Detection of calf muscle alterations in patients with chronic heart failure by P magnetic resonance spectroscopy: Impaired adaptation to continuous exercise.

Previous studies suggested that alteration of systemic skeletal muscle metabolism is a major determinant of exercise tolerance in patients with chronic heart failure (CHF). The authors examined calf muscle metabolism during continuous exercise of the foot in patients with CHF compared with normal subjects using (31)P magnetic resonance spectroscopy. The subjects were patients with New York Heart Association class II CHF who had previously suffered New York Heart Association class IV heart failure. Plantarflexion of the foot was repeated for 8 min 40 s at a rate of one contraction per second against a 2 kg load inside the magnet. At rest, during exercise (divided into the first one-half [EX1] and the latter one-half [EX2]) and at recovery, (31)P magnetic resonance spectroscopy data sets were acquired every 4 min 20 s. At rest, the phosphocreatine to hexamethylphosphoric triamide (PCr:HMPT) and the inorganic phosphate (Pi) to PCr ratios in the CHF group were not different from those in the normal group. During EX1 in the normal group, PCr levels decreased and Pi levels increased. Although exercise continued, these changes improved during EX2, suggesting there was an adaptation to exercise. The degree of change in the PCr:HMPT ratio during EX1 in the CHF group was not significantly different from that during EX1 in the normal group; however, the improvement during EX2 in the CHF group was impaired. The Pi:PCr ratio of EX1 to EX2 in the CHF group was significantly greater than that in the normal group (0.74+/-0.22 versus 0.19+/-0.05, respectively, P<0.005). Thus, in CHF, adaptation to continuous exercise may be impaired by alteration of skeletal muscle metabolism and this alteration may worsen exercise capacity.

Endothelial modulation and tolerance development in the vasorelaxant responses to nitrate of rabbit aorta.

We investigated the endothelial modulations in nitrate tolerance in isolated rabbit aorta. Nitrate tolerance was induced by a 72-h treatment with transdermal nitroglycerin (NTG, 0.4 mg/h) in conscious rabbits, which was verified by a 20-fold increase in the EC50 values [NTG tolerance (6.1 +/- 0.8) x 10(-7) M vs control (3.0 +/- 0.6) x 10(-8) M]. The relaxations to NTG in tolerant and nontolerant aortic strips were enhanced when their endothelia were denuded [E(-)]. In the presence of endothelium [E(+)], NTG-tolerant vessels were not tolerant to acetylcholine (ACh), which can release endothelial nitric oxide (NO), exogenous NO or 8-bromo (Br)-cGMP. In NTG-tolerant and nontolerant vessels with endothelium, concentration-response curves for NO were the same as those in endothelium-absent tolerant vessels. In both NTG-tolerant and nontolerant vessels, treatment with superoxide dismutase (SOD, 20 units/ml), an O2-. scavenger, unaffected the responses to NTG reduced in the presence of endothelium, but treatment with NG-nitro-L-arginine methyl ester (L-NAME, 10(-4) M), an NO synthase (NOS) inhibitor, reversed these reductions. Thus, our data did not indicate that an increased endothelial superoxide O2-. production contributes to nitrate tolerance. Our study suggested that (i) an impaired biotransformation process from NTG to NO is responsible for the occurrence of nitrate tolerance and (ii) vascular response to NTG enhanced by endothelial removal is related to blocked endothelial NO release.

Prognostic value of ECG-gated thallium-201 single-photon emission tomography in patients with coronary artery disease.

BACKGROUND: The phenomenon of reversible impairment in LV function has been well described and is known as myocardial stunning. OBJECTIVE: Thallium-201 myocardial perfusion gated SPECT was used to evaluate myocardial stunning and its incremental prognostic value in patients with coronary artery disease. PATIENTS AND METHODS: Fifty-six patients (aged 63+/-11 years) with coronary artery disease were included in this study. All subjects underwent exercise thallium scintigraphy. ECG-gated SPECT was obtained both at post-stress (10 minutes after the injection of 111 MBq of thallium at the time of peak exercise) and at rest (180 minutes). The left ventricular ejection fraction (LVEF) and end-systolic and end-diastolic volume (ESV, EDV) were determined by a quantitative gated SPECT (QGS) program. RESULTS: Follow-up was complete in all patients (mean 569 days). The magnitude of the depression of post-stress LVEF relative to the rest LVEF was correlated with the severity of ischemia (p < 0.05). The group with a median LVEF of more than 45% had a significantly higher event-free rate (p < 0.01). CONCLUSION: Assessment of post-stress left ventricular function by gated-SPECT provides incremental prognostic information and is useful in predicting cardiac events in patients with suspected or definite coronary artery disease.

Assessment of myocardial creatine concentration in dysfunctional human heart by proton magnetic resonance spectroscopy.

Creatine depletion in the non-viable infarcted human heart was previously demonstrated with proton magnetic resonance (MR) spectroscopy (1H MRS). In the present study, we assessed total creatine (CR) in human hearts with non-ischemic dysfunctions such as cardiomyopathy. Using cardiac-gated 1H MRS with MR image-guided PRESS localization, we measured septal CR in healthy and diseased human hearts. Fifteen patients with chronic heart failure (CHF, left ventricular ejection fraction < 45%) and 14 age-matched normal subjects were examined. Myocardial CR was significantly (p < 0.001) lower in failing hearts (15.1+/-SD 5.0 micromol/g wet weight, range 8.0-22.9) than in normal hearts (27.6+/-4.1 micromol/g wet weight, range 20.8-36.2). Myocardial CR concentrations in six heart failure patients with plasma B-type natriuretic peptide (BNP) levels of > 200 pg/ml (11.5+/-0.9 micromol/g wet weight, range 9.9-12.3) were significantly lower than those in four heart failure patients with plasma BNP levels of < 200 pg/ml (19.8+/-2.5 micromol/g wet weight, range 17.7-22.9, p < 0.001). Thus, our study showed that myocardial CR was decreased in non-ischemic dysfunctional hearts. Noninvasive measurements of myocardial CR by 1H MRS may be useful in the assessment of the severity of heart failure.

Myocardial creatine concentration in various nonischemic heart diseases assessed by 1H magnetic resonance spectroscopy.

BACKGROUND: Previous (31)P magnetic resonance spectroscopy (MRS) studies demonstrated that the myocardial phosphocreatine-to-ATP ratio offered important information concerning the degree of dysfunction and prognosis in patients with cardiomyopathy. In the present study, we investigated total creatine (CR) levels in various diseased hearts using 1H MRS. METHODS AND RESULTS: Fourteen patients with the following conditions were examined: cardiac amyloidosis (n = 2); hypertensive heart disease (4); valvular disease (2); hypertrophic cardiomyopathy (2); dilated cardiomyopathy (2); restrictive cardiomyopathy (1); and post-operative atrial septal defect (1). Myocardial CR was measured using 1H MRS with point-resolved spectroscopy localization. Overall, myocardial CR levels in diseased hearts were significantly lower than those in the control group [16.5+/-6.0 (n = 14) vs 27.1+/-3.2 micromol/g (n = 10), p < 0.001]. There was a positive correlation between myocardial CR and left ventricular ejection fraction (42.9+/-13.8%, range 19.5-69.1%) despite the different mechanisms of cardiac dysfunction (r = 0.60, p < 0.05). Myocardial CR levels in patients who were hospitalized due to heart failure within 1 year were significantly lower than those in other patients [11.3+/-1.0 (n = 4) vs 18.6+/-5.9 micromol/g (n = 10), p < 0.05]. CONCLUSIONS: Noninvasive measurement of myocardial CR using 1H MRS may be valuable in the assessment of disease severity and prediction of clinical course in various forms of heart disease.

Detection of metabolic abnormality in asynergic regions of ischemic human myocardium using 31P and 1H magnetic resonance spectroscopy.

To assess quantitatively phosphocreatine (PCr), adenosine triphosphate (ATP) and total creatine (CR) in asynergic regions of ischemic human myocardium using phosphorus (31P) and proton magnetic resonance spectroscopy (1H MRS). Patients were divided into two groups: 31P MRS and 1H MRS. In each group, patients were subdivided into three groups using echocardiography: a normokinetic [WN(P) (n = 6) in 31P MRS, WN(H) (n = 10) in 1H MRS], a hypokinetic [WH(P) (n = 13), WH(H) (n = 7)], and a- or dyskinetic wall motion groups [WA(P) (n = 14), WA(H) (n =6)]. They were compared with normal subjects of each group [CNP (n = 10), CN(H) (n = 10)]. 31P MRS spectra were obtained from the anterior and apical regions of the left ventricle by slice-selected 1D CSI. 1H MRS spectra were obtained from the 2 x 2 x 2-cm voxel set in the left ventricular wall by the PRESS method. In the 31P MRS group, myocardial PCr was significantly lower in the WH(P) and WA(P) groups than in the CN(P) group, but myocardial PCr in the WN(P) group did not differ from that in CN(P). A difference in ATP could not be detected among the four groups. In the 1H MRS group, myocardial CR was significantly lower in the WH(H) and WA(H) groups than in the CN(H) group. Myocardial CR in the WNH group did not differ from that in the CN(H). The noninvasive 31P and 1H MRS approach is useful in the assessment of metabolite reduction associated with wall motion abnormality.