SUMMARY. The relationship between coronary perfusion pressure and regional myocardial performance of the right ventricular free wall was studied, in the presence or absence of right ventricular hypertension in 13 open-chest dogs. The right coronary artery was perfused through a shunt from a carotid artery. Regional systolic shortening of the right ventricular free wall was measured by means of a sonomicrometric technique at various levels of coronary perfusion pressure. Regional shortening was insensitive to coronary perfusion pressure or flow when it was above 31 mm Hg or 0.27 ml/min per g. Once coronary perfusion was below this critical level, regional shortening in both base to apex and circumferential orientations decreased linearly, depending on the degree of perfusion pressure. Despite the presence of a monoexponential relationship between coronary perfusion pressure or flow and regional shortening, a direct linear relation between perfusion pressure and flow was consistently noted, with or without pulmonary artery banding, suggesting that there is limited autoregulation of right coronary flow. The critical perfusion pressure for maintaining regional myocardial function of the right ventricle was highly dependent on the level of right ventricular systolic pressure (r = 0.64 -0.72, P < 0.05). Thus, right ventricular systolic pressure was one of the important determinants of regional wall motion during coronary underperfusion. (Circ Res 57: 96-104, 1985) IN the left ventricle, severe coronary arterial stenosis reduces both coronary perfusion pressure and regional myocardial blood flow (Nakamura et al., 1973;Tomoike et al., 1977). This produces regional wall motion abnormalities (Wyatt et al., 1975;Nakamura et al., 1977; Koyanagi, 1979) and subsequent reductions in cardiac output if the ischemic zone is large enough (Lekven et al., 1973;Isoyama et al., 1983). The concept of critical flow below which regional contractile performance deteriorates in proportion to the reduction in perfusion has been documented repeatedly (Wyatt et al., 1975;Downey, 1976;Banka et al., 1977;Vatner, 1980;Weintraub et al., 1981). The critical level of perfusion pressure for maintaining normal regional wall motion in the left ventricle was about 40 to 60 mm Hg (Wyatt et al., 1975;Waters et al., 1977;Banka et al., 1977; Koyanagi, 1979). However, the relationship between coronary perfusion pressure and regional wall motion in the right ventricle remains poorly understood.Accordingly, in the present study, we examined the effects of graded reductions in regional coronary perfusion pressure on regional segment shortening in the right ventricular free wall. Because afterload influences the extent of regional wall motion during systole (Lekven and Kiil, 1975; Sasayama et al., 1980), segment shortening was measured with and without an increased level of right ventricular pressure induced by constricting the pulmonary artery. MethodsThirteen mongrel dogs (19-23 kg) were sedated with intramuscular morphine sulfate (10 mg) and then anest...
Transmural gradients related to myocardial cell death in the left ventricle have been explained by an uneven transmural distribution of myocardial collateral blood flow after coronary occlusion. 6 " 8 In the case of the right ventricle, several clinical observations 9 ' l0 and experimental studies"" 13 have shown that the evolution of myocardial necrosis in the right ventricular free wall is variable. However, the pathophysiology of the differences in myocardial infarction between right and left ventricles is not well understood. We attempted to define whether there is any topological difference in the evolution of myocardial necrosis through different transmural layers between right and left ventricles, with reference to risk area and regional myocardial blood flow. Materials and Methods Experimental Model and ProtocolFifty-one adult mongrel dogs of either sex (weight 16-29 kg) were anesthetized with sodium pentobarbital (25 mg/kg IV) and ventilated by room air and supplemental oxygen (2 1/min) via an endotracheal tube with a positive pressure respirator. A polyvinyl catheter was placed at the descending aorta through the carotid artery to monitor the aortic pressure and for reference blood sampling. The chest was opened in the left fourth intercostal space, and the heart was suspended in a pericardial cradle. The largest obtuse marginal branch of the left circumflex coronary artery as well as the main trunk of the right coronary artery (RCA) 2-3 cm distal to its orifice were dissected. These arteries were selected for obstruction because their perfusion areas are remote and comparable in size (Table 1).Catheter-tip manometers (PC-370, Miller Instruments) were placed in the left ventricular (LV) and right ventricular (RV) cavities through the femoral artery and femoral vein, respectively. After a control
ssessment of myocardial viability (MV) is importantto predict functional recovery and future cardiac events in patients with acute myocardial infarction (AMI). 1,2 Dobutamine stress echocardiography (DSE), in particular using low-dose dobutamine, is an excellent method for diagnosing MV and predicting the recovery of left ventricular dysfunction after MI, as well as in those patients who have undergone after revascularization for chronic ischemic heart disease. [3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18] 123 I-labelled 15-iodophenyl-3-R, S-methyl pentadecanoic acid (BMIPP) reflects the fatty acid utilization of the myocardium and is used with single-photon emission computed tomography (SPECT) for energy metabolism studies. 19 When myocardial ischemia occurs, there is prolonged impaired uptake of BMIPP. [19][20][21] Previous studies have demonstrated that concordant defects of perfusion and BMIPP scans represent scarred or non-viable tissue, a lower BMIPP uptake relative to perfusion (perfusion -BMIPP mismatch) indicates metabolically damaged but viable myocardium, and equivalently normal perfusion and BMIPP uptake represents normal or completely salvaged myocardium. 19,20,22,23 Furthermore, a perfusion -BMIPP mismatch is a good predictor of functional recovery after myocardial infarction. 23 Thus MV can be estimated by both DSE and dual-isotope simultaneous acquisition of myocardial perfusion with BMIPP. These methods, however, have their own merits and limitations, and have rarely been directly compared in the same patient following AMI to assess for their ability to diagnose MV and predict long-term functional recovery. 23 Methods Study PatientsThe study prospectively enrolled 35 consecutive patients (26 men, 9 women; mean age, 63±10 years) admitted with AMI between January 2000 and March 2001 who underwent both DSE and dual SPECT in the National Kyushu Medical Center. Diagnosis of AMI was based on typical chest pain lasting longer than 30 min, ST segment elevation Discordance between the 123 I-labelled 15-iodophenyl-3-R, S-methyl pentadecanoic acid (BMIPP) and 201 Tl findings may indicate myocardial viability (MV). This study compared dobutamine stress echocardiography (DSE) and single-photon emission computed tomography (SPECT) using the dual tracers for assessment of MV and prediction of functional recovery after acute myocardial infarction (AMI). DSE and dual SPECT were studied in 35 patients after AMI, of whom 28 underwent percutaneous coronary intervention in the acute stage. Dual SPECT was performed to compare the defect score of BMIPP and 201 Tl. The left ventricular wall motion score (WMS) was estimated during DSE and 6 months later to assess functional recovery of the infarct area. The rate of agreement of MV between dual SPECT and DSE was 89% (p<0.01), and the sensitivity and specificity of DSE for dual SPECT in MV assessment was 86% and 93%, respectively. The positive and negative predictive values for functional recovery by dual SPECT were 76% and 67%, respectively, and by DSE were 9...
Postprandial increase in remnant lipoprotein concentrations has been suggested as an important atherogenic factor. However, the influence of these remnants on the development of restenosis after percutaneous coronary intervention (PCI) remains to be examined. The present study was designed to address this point. In 60 consecutive patients with successful PCI, the influences of possible risk factors on the development of restenosis, including remnant-like particles (RLP) cholesterol (RLP-C) and triglyceride (RLP-TG), were examined. While mean concentrations of RLP-C and RLP-TG were normal in fasting state, postprandial change in RLP-C concentrations was a significant and independent risk factor for restenosis after PCI. The calculated cut-off index (COI) for the change was +64%. When the patients were divided into 2 groups according to this COI, minimal lumen diameter (MLD) and reference coronary diameter were comparable before and immediately after PCI between the high- (COI < 64%) and the low- (COI < 64%) responders. However, follow-up coronary angiography 3 to 6 months after PCI demonstrated that MLD, late loss, and loss index were all worse in the high responders compared with the low responders. These results indicate that post-prandial increase in RLP-C concentrations is an independent risk factor for restenosis after successful PCI, even in patients with normal fasting RLP-C levels.
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