Association of elevated plasma B-type natriuretic peptide levels with paroxysmal atrial fibrillation in patients with nonobstructive hypertrophic cardiomyopathy

Objectives: To investigate the relationship between the plasma B-type natriuretic peptide (BNP) level and the occurrence of atrial fibrillation (AF) in nonobstructive hypertrophic cardiomyopathy (HCM) patients. Methods: Patients (n=97) were classified into chronic AF (CAF; n=14), paroxysmal AF (PAF; n=18) and normal sinus rhythm (NSR; n=65) groups. The plasma BNP values were analyzed with logarithmic transformation. Results: The PAF group showed significantly higher plasma BNP levels than the NSR group [mean (range; -1 SD and +1 SD); 248.3 (143.5, 429.5) vs. 78.2 (27.9, 218.8 ng/L), p Conclusions: The present study indicated that plasma BNP level is clinically useful for identification of nonobstructive HCM patients who have a risk of PAF.</p

Prediction of acute left main coronary artery obstruction by 12-lead electrocardiography ST segment elevation in lead aVR with less ST segment elevation in lead V1

AbstractOBJECTIVESWe sought to determine the electrocardiographic (ECG) features associated with acute left main coronary artery (LMCA) obstruction.BACKGROUNDPrediction of LMCA obstruction is important with regard to selecting the appropriate treatment strategy, because acute LMCA obstruction usually causes severe hemodynamic deterioration, resulting in a less favorable prognosis.METHODSWe studied the admission 12-lead ECGs in 16 consecutive patients with acute LMCA obstruction (LMCA group), 46 patients with acute left anterior descending coronary artery (LAD) obstruction (LAD group) and 24 patients with acute right coronary artery (RCA) obstruction (RCA group).RESULTSLead aVR ST segment elevation (>0.05 mV) occurred with a significantly higher incidence in the LMCA group (88% [14/16]) than in the LAD (43% [20/46]) or RCA (8% [2/24]) groups. Lead aVR ST segment elevation was significantly higher in the LMCA group (0.16 ± 0.13 mV) than in the LAD group (0.04 ± 0.10 mV). Lead V1ST segment elevation was lower in the LMCA group (0.00 ± 0.21 mV) than in the LAD group (0.14 ± 0.11 mV). The finding of lead aVR ST segment elevation greater than or equal to lead V1ST segment elevation distinguished the LMCA group from the LAD group, with 81% sensitivity, 80% specificity and 81% accuracy. A ST segment shift in lead aVR and the inferior leads distinguished the LMCA group from the RCA group. In acute LMCA obstruction, death occurred more frequently in patients with higher ST segment elevation in lead aVR than in those with less severe elevation.CONCLUSIONSLead aVR ST segment elevation with less ST segment elevation in lead V1is an important predictor of acute LMCA obstruction. In acute LMCA obstruction, lead aVR ST segment elevation also contributes to predicting a patient’s clinical outcome

Factors influencing acute high-grade restenosis in emergency percutaneous transluminal coronary angioplasty for acute myocardial infarction.

We studied the factors which may induce acute high grade restenosis in emergency percutaneous transluminal coronary angioplasty (PTCA). PTCA was attempted in 50 patients with acute myocardial infarction, and the balloon catheter passed successfully across the occlusion site in 47 (94%) of the patients. These 47 patients were analyzed. &#34;Acute restenosis&#34; was defined as a lesion which was revascularized to less than 50% luminal reduction narrowed again to more than 75% luminal reduction 5 min after the balloon inflation. Univariate and multivariate analyses were used for determining factors which significantly influenced acute restenosis. The incidence of at least one restenosis episode was 45%. Multiple regression analysis selected 5 factors associated significantly with an increased rate of acute restenosis: 1) angiographic evidence of dissection, 2) lesion in the right coronary artery (RCA), 3) lack of or insufficient administration of thrombolytic agent preceding PTCA, 4) curved lesion and 5) relatively small balloon/artery diameter ratio. Acute restenosis correlated significantly with late reocclusion. This study indicates that it is important to administer a thrombolytic agent prior to emergency PTCA, and to use an adequately sized balloon to the artery when the acute restenosis occurs by using relatively smaller sized balloon. The present data also demonstrated that patients with RCA and a curved lesion have a relatively high risk of acute restenosis. This study indicates how patients with relatively high risk of acute restenosis may be identified.</p

Effect of heart rate and myocardial contractile force on coronary resistance.

The effect of the heart rate and myocardial contractile force on the extravascular resistance to blood flow of the left anterior descending coronary artery (LAD) was evaluated in 15 mongrel dogs anesthetized with sodium pentobarbital. The LAD was maximally dilated by intracoronary infusion of adenosine, which precluded the influence of vasomotor tone. Increases in the heart rate and myocardial contractile force decreased coronary blood flow in the absence of a change in coronary perfusion pressure. The changes in mean coronary resistance showed a significant linear relationship to changes in developed tension. The changes in coronary resistance caused by varying the heart rate and contractile force were so small that a normal coronary vascular tree could easily compensate for the increase in resistance. However, it is supposed that with critical stenosis of the vascular tree even a small increase in resistance might cause deleterious effects on coronary blood flow.</p

The contribution of adenylate cyclase to mycardial reactive hyperemia in the open-chest dog

Many lines of evidence suggest that adenosine partly regulates coronary vascular tone in response to myocardial ischemia after a brief coronary occlusion. However, the basic mechanisms of blood flow regulation of myocardial reactive hyperemia still remain unknown. This experiment was performed using the selective effect of forskolin to enhance the effects of agonists which exert receptor-mediated stimulation of adenylate cyclase. We exploited the potentiating effect of forskolin to test the hypothesis that activation of adenylate cyclase contributes to myocardial reactive hyperemia, especially by release of adenosine at the time of brief coronary occlusions. In ten open-chest dogs, intracoronary forskolin infusions, which produced plasma concentrations between 0.22 and 0.34 μM, slightly increased coronary blood flow and had no effect on hemodynamics or myocardial metabolism. Under these conditions, although peak reactive hyperemic flow rates were not affected, forskolin infusions reversibly increased repayments of flow debt significantly by 28, 25 and 27% following coronary occlusions of 15, 20 and 30 second, respectively (p<0.05). In other seven dogs, after observations of the effects of forskolin (0.16-0.26μM), 10μM of 8-phenyltheophylline, a potent adenosine antagonist, was intracoronarily infused simultaneously with forskolin. Forskolin potentiated debt repayments by about 23-27% following 15, 20 and 30 second occlusions. However, with simultaneous 8-phenyltheophylline, the effects of forskolin were eliminated significantly (p<0.05). The present results demonstrate that adenylate cyclase contributes to myocardial reactive hyperemia and adenosine has a significant role as metabolic regulator of reactive hyperemia through activation of adenylate cyclase