Reappraisal of functional importance of coronary collateral circulation

Coronary collateral circulation (CCC) is defined as an alternative blood-conveying circuit to the ischemic myocardium supplied by a jeopardized coronary artery. Accumulating evidence on CCC and its functional role has been derived from basic and clinical studies over several decades. Progress in molecular biology and genetic engineering has enabled us to elucidate the mechanisms of collateral growth on the basis of the development of new experimental models and methods for accurate assessment of CCC. These achievements in basic research have been promptly translated into the clinical setting. Interaction between basic and clinical sciences in the fascinating field of CCC will contribute to the establishment of innovative collateral-promoting therapy for severe coronary artery disease.     

The functional significance of coronary collateral circulation during sudden coronary occlusion]

The functional significance of the coronary collateral circulation remains controversial. It has been suggested that collateral circulation possibly helps prevent myocardial ischemia. Seventeen target lesions in 15 patients were studied to determine the relationship between the extent of the coronary collateral circulation and the degree of ventricular dysfunction during percutaneous transluminal coronary angioplasty (PTCA). During the first balloon inflation, diastolic indices such as left ventricular end-diastolic pressure, max negative dP/dt and the time constant of early relaxation were measured immediately before and at 60 sec following balloon inflation. During the second inflation, the contralateral and ipsilateral collateral circulations were evaluated. The latter was graded as follows: 0 = none; I = filling of side branches only; II = partial filling of the epicardial segment; and III = complete filling of the epicardial segment. Following balloon inflation, a significant increase was noted in the time constant of early relaxation in patients with grade 0 collateral circulation (40 +/- 7 to 47 +/- 7 msec: p < 0.01) and grade II collateral circulation (52 +/- 12 to 56 +/- 13 msec: p < 0.05). The percent increase in the time constant of early relaxation of patients with grade 0 and I collateral circulations exceeded that of patients with grade II (p < 0.05) or grade III collateral circulation (p < 0.05). Left ventricular end-diastolic pressure was elevated in all groups during PTCA. There was no significant difference in the percent increase of left ventricular end-diastolic pressure (LVEDP) between the 4 groups. However, LVEDP before PTCA was higher in patients with grade III collateral circulation than in patients in the other groups. Max negative dP/dt did not change significantly in any group. In conclusion, collateral circulation helps prevent myocardial ischemia during acute coronary occlusion, which is most precisely shown by the time constant of early relaxation. The degree of this protective function of collateral circulation seems to vary.     

Reappraisal of the functional significance of the coronary collateral circulation.

A review of data in 465 patients with complete obstruction of either the left anterior descending or right coronary artery was undertaken to evaluate the functional role of the collateral circulation. Complete obstruction of a dominant right coronary artery was observed in 288 patients, 83 percent with distal filling and visualization of the posterior descending artery by way of collateral vessels. Complete obstruction of the left anterior descending artery was noted in 177 patients, 71 percent with filling and visualization distal to the obstruction by way of collateral vessels. Among patients with obstruction of the left anterior descending artery, there was a significantly greater frequency of congestive heart failure and cardiomegaly in those without collateral vessels than in those with collateral vessels. The former also had a significantly greater frequency of both electrocardiographic evidence of an anterior wall myocardial infarction and angiographic findings of anterior wall asynergy. The frequency of inferior myocardial infarction and inferior wall asynergy was not influenced by the presence of collateral vessels. These observations indicate that the collateral circulation plays a significant protective role in the presence of obstruction of the left anterior descending artery, which is not apparent with obstruction of the right coronary artery.     

严重冠脉病变侧支循环形成影响因素探讨

目的：探讨严重冠脉病变侧支循环影响因素。方法：对79例冠脉狭窄≥90％和（或）闭塞病变血管造影进行分析。结果：79例严重冠脉病变有68例见侧支循环，其中右冠病变47例，伴侧支循环44例，占93．61％（44／47），前降支病变51例，伴侧支循环29例，占56．86％（29／51），回旋支病变26例，伴侧支循环20例，占76．92％（20／26），合并糖尿病39例，37例伴侧支循环，非糖尿病40例，31例伴侧支循环（P＜0．05），合并高血压组49例，46例伴侧支循环，非高血压组30例，22例伴侧支循环（P＜0．01）。结论：严重冠脉慢性病变多数建立侧支循环，以右冠病变显著，糖尿病（或）高血压促进侧支循环建立。     

Evaluation of coronary collateral circulation in conscious humans

The physiologic importance of coronary collateral vessels was investigated in 19 men undergoing transient proximal occlusion of the left anterior descending (LAD) branch without sedative medication. No vasodilators were given before LAD balloon occlusion. Six men had angiographic filling of the LAD via coronary collateral vessels (Group 1) and 13 did not (Group 2). Aortic, distal coronary and left ventricular (LV) filling pressures and great cardiac vein blood flow (thermodilution) were recorded continuously during occlusion. During LAD occlusion, clinical and electrocardiographic evidence for transient myocardial ischemia occurred more often in patients in Group 2 than in Group 1, but the difference was not statistically significant. Heart rate and aortic and distal coronary pressures were similar in Groups 1 and 2. LV filling pressure was 3 mm Hg higher in Group 2 patients (p less than 0.05). The aortic to distal coronary pressure difference and the distal coronary to LV filling pressure difference were also similar in Groups 1 and 2. However, residual great cardiac vein flow was 55% higher (p less than 0.05) and the calculated coronary collateral resistance index was 45% lower in patients in Group 2 compared with those in Group 1 (p less than 0.01). Coupling of regional coronary venous blood flow estimates to pressure measurements routinely made during angioplasty is a new technique that allows evaluation of determinants of coronary collateral function in conscious humans.(ABSTRACT TRUNCATED AT 250 WORDS)     

Vasopressin and the mature coronary collateral circulation

In isolated vascular rings, we have shown that mature coronary collateral vessels are highly responsive to the vasoconstrictor effects of vasopressin. The purpose of the present study was to determine the effect of concentrations of vasopressin encountered in pathophysiologic states on the collateral circulation in vivo. We studied eight open-chest anesthetized dogs with mature coronary collateral vessels 3-6 months after placement of an ameroid constrictor on the left circumflex coronary artery. The left anterior descending coronary artery was perfused at constant pressure, and peripheral coronary pressure was monitored continuously throughout each experiment. At baseline and during intracoronary infusion of vasopressin, which resulted in concentrations ranging from 8 +/- 3 to 1,340 +/- 327 microM/ml, we measured regional myocardial perfusion with radiolabeled microspheres. At baseline, regional myocardial perfusion to the collateral-dependent myocardium and to the normally perfused myocardium was similar; however, during vasopressin infusion, collateral-dependent zone flow decreased by 49 +/- 14% whereas normal zone flow decreased by only 9 +/- 9% (p less than 0.0005, normal zone perfusion vs. collateral perfusion). Vasopressin increased transcollateral resistance by 242 +/- 95% above baseline but produced a more modest increase in normal zone resistance (15 +/- 10%). The subendocardial to subepicardial perfusion ratio increased by 28 +/- 12% in the normal zone in response to vasopressin but decreased by 18 +/- 11% in the collateral-dependent zone. These data show that mature coronary collateral vessels are responsive to the vasoconstrictor effects of vasopressin at concentrations encountered in various pathophysiologic states.(ABSTRACT TRUNCATED AT 250 WORDS)