Peter J. Sabia

An association between collateral blood flow and myocardial viability in patients with recent myocardial infarction

BACKGROUND We hypothesized that successful reperfusion of an occluded infarct-related coronary artery even late after acute myocardial infarction would result in improved regional wall motion and that such improvement might be related to the presence of collateral blood flow within the infarct bed. METHODS We assessed regional wall motion by two-dimensional echocardiography at base line and one month after angioplasty was attempted in the occluded infarct-related artery in 43 patients who had had a myocardial infarction two days to five weeks earlier. A wall-motion score was assigned to each patient on a five-point scale (from 1 [normal function] to 5 [dyskinesia]). The percentage of the infarct bed perfused by collateral flow was assessed with myocardial contrast echocardiography. RESULTS In the 41 patients who had abnormal wall motion at base line, improvement in function was noted in 25 (78 percent) of the 32 in whom angioplasty was successful, as compared with only 1 (11 percent) of the 9 in whom it was unsuccessful (P < 0.001). The percentage of the infarct bed supplied by collateral flow at base line was directly correlated with wall function and inversely correlated with the wall-motion score one month after successful angioplasty (r = -0.64, P < 0.001). Among the patients in whom angioplasty was successful, the 23 in whom > 50 percent of the infarct bed was supplied by collateral flow had better wall motion (P < 0.001) and greater improvement in wall motion at one month (P = 0.004) than the 9 in whom < or = 50 percent of the bed was supplied by collateral flow. The degree of improvement in function was not influenced by the length of time between the infarction and the attempted angioplasty. CONCLUSIONS The myocardium remains viable for a prolonged period in many patients with acute infarction and an occluded infarct-related artery. Viability appears to be associated with the presence of collateral blood flow within the infarct bed.

Functional significance of collateral blood flow in patients with recent acute myocardial infarction. A study using myocardial contrast echocardiography.

BackgroundWe hypothesized that myocardial contrast echocardiography (MCE) can be used to both measure collateral blood flow as well as assess the functional significance of collaterals in patients with acute myocardial infarction (AMI). Methods and ResultsMCE was performed in 33 patients with recent AMI (12±7 days) and an occluded infarct-related artery (IRA), both before and after attempted percutaneous transluminal coronary angioplasty (PTCA). The size of the occluded bed was defined in patients with successful PTCA by injecting contrast directly into the opened IRA and expressed as a percent of the myocardium in the short-axis view. The percent of the perfusion bed supplied by collaterals before PTCA was determined. Transit rates of the microbubbles within the collateralized regions were also measured and were expressed as a percent of the transit rates in the normal adjacent beds. Regional function within the occluded bed was assessed using echocardiography and was graded as 1 (normal) to 5 (dyskinetic). Collaterals were graded on coronary angiography as 0 (none) to 3 (abundant). The perfusion bed size was larger for the left anterior descending (LAD) than for the right (RCA) and left circumflex (LCx) coronary arteries (37±6% versus 27±12% of the myocardium, p=0.02). The percent of the occluded bed supplied by collateral flow was greater for RCA and LCx compared with the LAD (87±301% versus 72±22%, p<0.01). There was poor correlation between MCE-defined percent of occluded bed supplied by collaterals and angiographic collateral grade (r=0.13). Regions supplied by collaterals were less likely to show confluent hypoperfused zones after reperfusion compared with those not supplied by collaterals. Similarly, the percent ofmyocardium not perfused by either anterograde or collateral flow correlated well (r=0.67, p<0.01) with peak creatine kinase levels and was more likely to be associated with Q waves. Finally, although there was poor correlation between angiographic collaterals and regional function (r=0.20), there was a significant negative correlation between MCE-defined spatial extent of collateral flow and regional function (r=−0.57, p<0.01). ConclusionsMCE can be used to measure collateral flow in patients with recent AMI and to assess the functional significance of collaterals in these patients. This technique may be ideally suited for the assessment of collateral perfusion in patients undergoing cardiac catheterization.

Importance of two-dimensional echocardiographic assessment of left ventricular systolic function in patients presenting to the emergency room with cardiac-related symptoms.

BackgroundThis prospective study was designed to test the hypothesis that the assessment of left ventricular systolic function at the time of emergency room (ER) presentation provides valuable diagnostic and prognostic information in patients with cardiac-related symptoms. Methods and ResultsThe study is based on a 2-year follow-up of 171 consecutive patients evaluated in the ER for such symptoms. In the course of follow-up, one third of the patients (55 of 171) suffered a major cardiac event. For those with left ventricular systolic dysfunction (LVSD), the age-adjusted rate of early events (occurring within 48 hours of presentation) was more than eight times higher than for those without LVSD (26.9% versus 3.3%, p < 0.01). For events occurring after 48 hours of ER presentation, LVSD was associated with a nearly fourfold excess of cardiac events (23.9% versus 6.4%, p < 0.01). Other than advanced age, the most important confounder for early events included an abnormal electrocardiogram diagnostic for acute myocardial infarction. Confounders for late events included advanced age and a history of hypertension. LVSD on two-dimensional echocardiography (2DE) was the only finding associated with early and late events after controlling for other risk factors. In addition, the prediction of these events derived from the combination of historical, clinical, electrocardiographic, and 2DE findings was significantly improved when accounting for the presence or absence of LVSD (p < 0.01). ConclusionsWe conclude that the 2DE assessment of left ventricular systolic function provides valuable diagnostic and prognostic information in subjects presenting to the ER with cardiac-related symptoms.

Value of Two-dimensional Echocardiography for Determining the Basis of Hemodynamic Compromise in Critically Ill Patients: A Prospective Study

We postulated that because the first step in the management of critically ill patients with hypotension, pulmonary edema, or both is to determine whether the cause is cardiac or noncardiac, direct visualization of the heart with two-dimensional echocardiography would be useful for determining the basis of hemodynamic compromise in such patients. Accordingly, 49 consecutive patients (33 men and 16 women; mean age 61 +/- 15 years) underwent two-dimensional echocardiography within 2 hours of placement of a pulmonary artery flotation catheter for determining the reason for hypotension, pulmonary edema, or both. To discriminate between cardiac and noncardiac causes, hemodynamic and two-dimensional echocardiographic data were evaluated independently by two to three blinded interpreters based on predetermined criteria. There was complete agreement between pulmonary artery catheter and two-dimensional echocardiographic data in 36 (86%) of the 42 patients in whom interpretable data were available in terms of cardiac versus noncardiac causes. The two modalities agreed in all patients with hypotension alone and disagreed in 2 of the 20 patients with pulmonary edema alone and 4 of the 14 patients with combined hypotension and pulmonary edema. In cases of discordance, the two tests provided complimentary information, particularly in patients with sepsis in whom the stroke volume may be normal to high but left ventricular systolic function may be depressed. The time taken for pulmonary artery catheter placement was 63 +/- 45 minutes versus 19 +/- 7 minutes for two-dimensional echocardiography.(ABSTRACT TRUNCATED AT 250 WORDS)

Value and Limitations of Current Methods of Evaluating Patients Presenting to the Emergency Room with Cardiac-Related Symptoms for Determining Long-Term Prognosis

The goal of this study was to determine the value and limitations of the current approach for evaluating patients in the emergency room (ER) with cardiac-related symptoms in terms of predicting long-term outcome. Accordingly, 274 consecutive prospectively identified patients presenting to the ER with such symptoms were evaluated, and follow-up was obtained at 20 +/- 9 months in 265 of them (97%). Adverse cardiovascular events were defined as: nonfatal myocardial infarction, death, cerebrovascular accident with neurologic deficit, life-threatening arrhythmia and cardiac surgery. Eighty-three patients (31%) had a cardiovascular event during follow-up; 42 occurred within 48 hours of ER presentation, whereas 41 occurred in the ensuing months. Findings on physical examination and electrocardiogram provided additional prognostic information, compared with that of history alone, when added sequentially into a Cox model. However, by discriminant function analysis, only 63% of actual events were correctly predicted by the model. Events occurring after 48 hours of ER presentation were correctly predicted only 50% of the time compared with those occurring within 48 hours of ER presentation, which were correctly predicted 75% of the time (p = 0.04). It is concluded that patients presenting to the ER with cardiac-related symptoms are at high risk for adverse cardiovascular events. The likelihood of an event occurring after 48 hours of presentation is as high as one occurring within 48 hours. Current methods of evaluating such patients have limited prognostic value, particularly for those at long-term risk for events.

Effects of late (1 to 30 days) reperfusion after acute myocardial infarction on the signal-averaged electrocardiogram

Early reperfusion (4 to 6 hours) after acute myocardial infarction reduces mortality and reduces the incidence of late potentials on a signal-averaged electrocardiogram (SAECG). Recent reports suggest that reperfusion accomplished after > 6 hours also may reduce mortality. The effect of such later reperfusion on the SAECG is not known. We hypothesized that reperfusion by angioplasty accomplished > 24 hours after onset of infarction would reduce late potentials and improve the parameters on the SAECG. Forty-one patients with a totally occluded infarct-related artery 12 +/- 8 days after infarction underwent attempted angioplasty. SAECG, echocardiography and thallium-201 imaging were performed before and 1 month after attempted angioplasty. Angioplasty resulted in successful reperfusion in 32 patients and was unsuccessful in 9. No change in the incidence of late potentials occurred after successful reperfusion (13 of 32 patients before and 13 of 32 patients 1 month later) or after unsuccessful reperfusion (6 of 9 patients before and 5 of 9 patients 1 month later). Among patients with successful reperfusion, no significant change occurred in the QRS duration or the terminal signal duration < 40 microV. The terminal root-mean-square voltage in microvolts improved significantly at 1 month (31 +/- 25 before to 38 +/- 29 after, p = 0.004). Twenty-two of 32 patients with successful reperfusion had improved wall motion in the infarct zone at 1 month. Despite an improvement in function in these patients, no change in the incidence of late potentials occurred by 1 month.(ABSTRACT TRUNCATED AT 250 WORDS)