Objective-To decrease pre-hospital delay in patients with chest pain. Design-Population based, prospective observational study. Setting-A province of Switzerland with 380 000 inhabitants.

Coronary angiography demonstrates only collateral arteries that are already in use (spontaneously visible collaterals). Percutaneous transluminal coronary angioplasty (PTCA) provides an opportunity to uncover collaterals ready to become functional in case of occlusion of the recipient artery (recruitable collaterals). spontaneously visible on a routine coronary angiogram and with that of recruitable collaterals. MethodsDefinitions. The coronary wedge pressure was defined as the mean distal coronary pressure measured through the central lumen of a balloon catheter during a complete occlusion of the artery for at least 30 sec. It was rounded to the next value divisible by five. The transocclusional pressure gradient was defined as the difference between the mean aortic pressure measured through the guiding catheter at the coronary orifice and the simultaneous coronary wedge pressure. The transstenotic pressure gradient was defined as the difference between the mean pressure distal to the lesion (measured at the tip of the empty balloon catheter situated in the lesion) and the simultaneous mean pressure in the coronary ostium. The degree of stenosis was indicated as a visual estimate of diameter reduction.Only collaterals filling at least a segment of the recipient vessel distal to the lesion were considered. Spontaneously visible collaterals were defined as collaterals documented by routine coronary angiography (performed after sublingual or during intravenous nitroglycerin administration). Recruitable collaterals were defined as collaterals not visible on the routine angiogram but visible during proximal balloon occlusion of the recipient coronary artery. Ipsilateral collaterals connect two vessels with a common coronary ostium, e.g., the left anterior descending coronary artery with the circumflex coronary artery or the right ventricular branch with the posterior descending CIRCULATION 906

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Coronary wedge pressure is the pressure recorded distal to a stenosis while the inflated balloon occludes the coronary artery during angioplasty. This pressure has been shown to reflect actual (visible) and potential (recruitable) collateral flow to the stenosed artery, distal to the angioplasty site. In 100 consecutive vessels (91 patients) for which coronary wedge pressure had been measured at the time of angioplasty, the long-term (7 +/- 3 months) angiographic results was evaluated. The overall angiographic restenosis rate was 37%. It was 52% (25 of 48) in arteries with a coronary wedge pressure greater than or equal to 30 mm Hg and 23% (12 of 52) in arteries with a coronary wedge pressure less than 30 mm Hg (p less than 0.01). The mean coronary wedge pressure was 30 +/- 10 mm Hg for vessels with restenosis and 26 +/- 9 mm Hg for those without restenosis (p less than 0.01). The prevalence of angiographically visible collateral flow was 42% and 29%, respectively (p = NS). Neither age, sex, presence of unstable angina, left ventricular function, number of diseased vessels nor initial and final transstenotic pressure gradient and degree of stenosis were significantly associated with the long-term outcome after angioplasty. Restenosis rate is significantly increased when coronary wedge pressure measured at the time of angioplasty is high (greater than or equal to 30 mm Hg). This suggests a negative influence of competitive collateral flow on long-term results of angioplasty.

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