Anthony Fung

The physiologic basis of dobutamine as compared with dipyridamole stress interventions in the assessment of critical coronary stenosis

Noninvasive cardiac imaging with echocardiography or thallium-201 scintigraphy utilizing pharmacologic agents as alternatives to exercise is gaining popularity. We investigated the physiologic rationale underlying the optimal choice of pharmacologic stress for functional versus perfusion imaging. With the use of an open-chest dog model, a critical stenosis of the left circumflex coronary artery was produced with total ablation of hyperemic response to a 15 sec period of complete occlusion. Regional left ventricular wall thickening was assessed by quantitative two-dimensional echocardiography. Regional myocardial blood flow was determined by microspheres in both the flow-restricted left circumflex area and the control area supplied by the left anterior descending artery. Eight dogs received 15 micrograms/kg/min dobutamine intravenously for 10 min, and nine dogs received 0.14 mg/kg/min dipyridamole intravenously for 4 min. Dobutamine induced wall thickening abnormalities in all dogs while dipyridamole induced dysfunction in only 55% of the animals studied (p less than .01). Subendocardial blood flow to the left circumflex area was unchanged after both dobutamine and dipyridamole when compared with baseline blood flow. However, subendocardial blood flow increased markedly after dipyridamole in the control area. Regional subendocardial blood flow ratio (left anterior descending/left circumflex) was 3.74 +/- 0.09 (mean +/- SEM) after dipyridamole versus 1.27 +/- 0.09 after dobutamine (p less than .001).(ABSTRACT TRUNCATED AT 250 WORDS)

Value of percutaneous transluminal coronary angioplasty after unsuccessful intravenous streptokinase therapy in acute myocardial infarction

The effect of sequential high-dose intravenous streptokinase (SK) (1.5 million units) followed by emergency percutaneous transluminal coronary angioplasty (PTCA) on preserving left ventricular function was assessed prospectively in 34 patients with acute myocardial infarction (AMI). Intravenous SK therapy was initiated 2.6 +/- 1.3 hours (mean +/- standard deviation) after the onset of chest pain. Urgent coronary angiography showed persistent total occlusion in 13 patients, significant diameter stenosis (70 to 99%) in 18 patients and a widely patent artery (less than 50% stenosis) in 3 patients. Emergency PTCA was performed in 29 patients 5.0 +/- 2.1 hours after symptom onset. Successful recanalization was achieved in 33 of the 34 patients (97%) treated with sequential therapy. Repeat contrast ventriculograms recorded 7 to 10 days after intervention in 23 patients showed that the left ventricular ejection fraction increased from 53 +/- 12% to 59 +/- 13% (area-length method, p less than 0.002). Regional wall motion of the infarcted segments improved from -2.7 +/- 1.1 to -1.5 +/- 1.7 SD/chord (centerline method, p less than 0.003). In the subgroup of patients with an occluded artery on initial angiography (group A, n = 10), both global left ventricular ejection fraction (49 +/- 12% vs 59 +/- 12%, p less than 0.002) and regional wall motion (-3.2 +/- 1.0 vs -1.9 +/- 1.7 SD/chord, p less than 0.002) improved significantly. In contrast, no significant improvement was seen in patients with a patent artery on initial angiography (n = 13). Thus, sequential intravenous SK and emergency PTCA is efficacious in achieving coronary reperfusion and in improving both global and regional left ventricular function.(ABSTRACT TRUNCATED AT 250 WORDS)

Prevention of subsequent exercise-induced periinfarct ischemia by emergency coronary angioplasty in acute myocardial infarction: comparison with intracoronary streptokinase.

To compare the efficacy of emergency percutaneous transluminal coronary angioplasty and intracoronary streptokinase in preventing exercise-induced periinfarct ischemia, 28 patients presenting within 12 hours of the onset of symptoms of acute myocardial infarction were prospectively randomized. Of these, 14 patients were treated with emergency angioplasty and 14 patients received intracoronary streptokinase. Recatheterization and submaximal exercise thallium-201 single photon emission computed tomography were performed before hospital discharge. Periinfarct ischemia was defined as a reversible thallium defect adjacent to a fixed defect assessed qualitatively. Successful reperfusion was achieved in 86% of patients treated with emergency angioplasty and 86% of patients treated with intracoronary streptokinase (p = NS). Residual stenosis of the infarct-related coronary artery shown at predischarge angiography was 43.8 +/- 31.4% for the angioplasty group and 75.0 +/- 15.6% for the streptokinase group (p less than 0.05). Of the angioplasty group, 9% developed exercise-induced periinfarct ischemia compared with 60% of the streptokinase group (p less than 0.05). Thus, patients with acute myocardial infarction treated with emergency angioplasty had significantly less severe residual coronary stenosis and exercise-induced periinfarct ischemia than did those treated with intracoronary streptokinase. These results suggest further application of coronary angioplasty in the management of acute myocardial infarction.

Early reperfusion therapy improves left ventricular function after acute inferior myocardial infarction associated with right coronary artery disease

Quantitative global and regional ventriculographic analysis was performed acutely and 1 week later in 46 patients undergoing reperfusion procedures within 6 hours of acute inferior myocardial infarction due to right coronary artery disease. While serial improvement in global left ventricular ejection fraction was not demonstrated for the group, infarct zone regional wall motion did improve (-2.7 +/- 0.9 vs -2.3 +/- 1.4 SD/chord, p less than 0.007). Serial improvement in global ejection fraction was demonstrated in the subgroup of patients treated within 2 hours of symptom onset (55 +/- 10 vs 62 +/- 10%; n = 5; p less than 0.03). Infarct zone regional wall motion improved serially only in the subgroup of patients treated within 3 hours of symptom onset (-2.4 +/- 1.1 vs -1.3 +/- 1.7 SD/chord; n = 11; p less than 0.007). Patients with initially patent arteries had a higher ejection fraction on follow-up catheterization than did those with initially occluded vessels (61 +/- 11 vs 55 +/- 7%; p less than 0.02), and patients with patent arteries at follow-up had a higher ejection fraction than did those whose arteries were occluded (60 +/- 9 vs 48 +/- 4%; p less than 0.0001). We conclude that significant improvement in global and regional left ventricular function in patients with inferior myocardial infarction is possible when reperfusion therapy is begun early or when arterial patency is achieved.

The prognostic impact of revascularization strategy in acute myocardial infarction and cardiogenic shock: Insights from the British Columbia Cardiac Registry

In patients with acute myocardial infarction (AMI) and cardiogenic shock (CS), percutaneous coronary intervention (PCI) of the culprit vessel is associated with improved outcomes. A large majority of these patients have multivessel disease (MVD). Whether or not PCI of non‐culprit disease in the acute setting improves outcomes continues to be debated. We evaluated the prognostic impact of revascularization strategy for patients presenting with AMI and CS.

INSIGHTS FROM REGISTRY DATA: WHY DO BLEEDING HEARTS DIE?

Mortality post-PCI occurs more frequently in patients receiving a blood transfusion. The mechanism responsible for this is unclear. We examined the time course between PCI and death in patients dying within 30 days of PCI, comparing transfused and non-transfused patients.nnOf 32,580 patients