Significance of Collateral Circulation in Patients With Left Main Coronary Artery Disease

Influence of coronary collateral vessels on myocardial infarct size in humans. Results of phase I thrombolysis in myocardial infarction (TIMI) trial. The TIMI Investigators

BACKGROUND

The influence of coronary collateral vessels on infarct size in humans remains controversial, partly because no previous study has examined the impact of collaterals present at the onset of acute myocardial infarction on infarct size.

METHODS AND RESULTS

The present study used the data base of the Thrombolysis in Myocardial Infarction (TIMI) Phase I trial to correlate the presence or absence of angiographically documented collaterals in the initial hours of myocardial infarct evolution with the size of the infarct as assessed by serial measurements of serum creatine kinase (CK). To avoid the confounding effects of reperfusion on enzymatic estimates of infarct size, this report is limited to those 125 patients who failed to recanalize at 90 minutes after administration of tissue plasminogen activator or streptokinase. Patients with angiographically documented collaterals (group A, n = 51) had significantly lower values of peak serum CK than patients without collaterals (group B, n = 74) (1,877 +/- 216 versus 2,661 +/- 212 IU/l, respectively [mean +/- SEM], p = 0.004). Similarly, CK-derived infarct size estimates were significantly lower in group A than in group B (20.6 +/- 2.5 versus 31.4 +/- 2.8 CK gram equivalents, p = 0.001). The infarct size observed in patients with collaterals was less for anterior infarctions as well as for infarctions of other locations; thus, the beneficial effects of collaterals were independent of the site of the infarct. In 65 of the 125 patients who failed to reperfuse, left ventricular ejection fraction (LVEF) was assessed by contrast ventriculography both at initial cardiac catheterization (before thrombolytic therapy) and at hospital discharge. Among the patients who had both studies, global LVEF tended to increase from pretreatment to hospital discharge in group A (from 50.6 +/- 1.8% to 53.4 +/- 1.8%, p = 0.10) but decreased in group B patients (from 50.3 +/- 1.8% to 47.8 +/- 1.7%, p = 0.02). At hospital discharge, global LVEF was greater in patients with coronary collaterals (53.5 +/- 1.7% versus 49.6 +/- 1.7%, p = 0.01).

CONCLUSIONS

The results demonstrate that, in patients in whom thrombolytic therapy fails to induce reperfusion, the presence of coronary collateral vessels at the onset of myocardial infarction is associated with limitation of infarct size as assessed enzymatically and with improved ventricular function on discharge as assessed by LVEF.

Preservation of left ventricular function in patients with total occlusion of the left anterior descending coronary artery and wide-caliber distal vessel filling by collateral vasculature

The segmental ventricular function of 76 patients with total occlusion of the left anterior descending coronary artery (LAD) was analyzed to establish the relationship between ventricular function and the presence and angiographic appearance of the collateral circulation. The relationship between function and collateral supply was found to be significant (P less than .01). The only angiographic feature of the collateral vasculature that was associated with preserved function was the caliber of the distal LAD. Wide-caliber vessels were more likely to be associated with preserved ventricular function than thin vessels (P less than .01). In contrast, both rapidly filling collateral arteries and slow filling vessels were associated with preserved ventricular function. Collateral supply maintenance was significantly associated with preserved ventricular function, even when the collaterals arose from stenotic coronary arteries. Furthermore, despite marked differences in ventricular function between the base and apex of the heart, there was a true relationship between preserved ventricular function and the presence of collateral vessels for all segments of the anterior wall. These findings may be relevant to clinical decision making and to proper interpretation of studies of ventricular function following LAD occlusion.

Effects of coronary artery narrowing, collaterals, and left ventricular function on the pattern of myocardial perfusion

We evaluated effects of the degree of diameter narrowing of the coronary arteries (50-69%, 70-89%, greater than or equal to 90%); extent of coronary disease [one-vessel disease (1VD), two-vessel (2VD), three-vessel (3VD)]; collaterals; and left ventricular function on the pattern of exercise thallium-201 perfusion in 121 patients; 30 patients with normal coronary angiograms, 37 with 1VD, 24 with 2VD, and 30 with 3VD. Fifteen patients had Q waves on ECG, 29 patients had akinetic segments on the left ventriculogram, and 46 patients had collaterals. The results suggest the following: 1) Patients with 59-69% narrowing of one vessel have normal exercise perfusion. 2) All patients with 1VD have abnormal exercise perfusion if the degree of narrowing is greater than or equal to 90%, unless the right coronary artery (RCA) is the vessel involved. 3) Patients with 2VD and 3VD generally have abnormal exercise perfusion unless all the narrowings are < 90%, or the RCA is the only vessel with greater than or equal to 90% narrowing, or the stress is submaximal. 4) Collaterals do not protect against development of abnormal exercise perfusion; they feed the most severely narrowed vessel, and perfusion abnormalities are ordinarily seen in the distribution of such severely narrowed vessels. 5) Neither the presence of Q waves on the ECG nor an akinetic segment on the left ventriculogram correlates with defects in the redistribution images; residual defects may be seen in the delayed images despite the absence of prior myocardial infarction, and normal images may be seen despite the presence of akinetic segments in the left ventriculogram.

Survival with total occlusion of the left main coronary artery. Significance of the collateral circulation

Four patients with total occlusion of the left main coronary artery are described. Angina pectoris was severe (NYHA class 3--4) and had lasted 20 months to seven years. Three patients had experienced a myocardial infarction. All displayed large collaterals arising from a nearly normal right coronary artery and feeding both the left anterior descending and the left circumflex arteries. The left ventricular ejection fractions ranged from 20% to 65%, and all patients had varying degrees of left ventricular asynergy. Coronary artery bypass surgery resulted in a marked improvement in three patients; one patient who underwent an aneurysmectomy died two months after the operation. The data show that total occlusion of the left main coronary artery is compatible with survival if adequate collateral supply develops from the right coronary artery. In this rare angiographic subset collateral circulation is clearly functionally significant.