New support for clarifying the relation between ST segment resolution and microvascular function: degree of ST segment resolution correlates with the pressure derived collateral flow index.

OBJECTIVE To investigate the relation between the degree of ST segment resolution (STR) after thrombolysis and the pressure derived collateral flow index (CFIp), determined using an intracoronary pressure measurement technique in patients with recent myocardial infarction. METHODS 33 patients were studied. TIMI grade III flow was achieved in the infarct related artery by thrombolysis. A surface ECG was obtained on admission and 90 minutes later. The sum of ST segment elevations was measured by summing all leads with ST elevation on the baseline ECG and on the 90 minute ECG (after thrombolysis) and calculating the percentage recovery. The study population was divided into two groups, with good STR (> or = 50%; group 1) or poor STR (< 50%; group 2). After angiography, a fibreoptic pressure monitoring guidewire was advanced to the stenosis to be dilated. The CFIp was determined as the ratio [coronary wedge pressure - central venous pressure]/[mean aortic pressure - central venous pressure]. RESULTS The mean STR on the surface ECG was 54.6% and mean (SD) CFIp was 0.25 (0.12) (range 0.10-0.41). There was an inverse correlation between the individually calculated percentage of STR and CFIp (r = -0.64, p < 0.01). The mean CFIp was lower in patients with a good STR than in those with a poor STR (0.18 (0.07) v 0.27 (0.10), p < 0.02). CONCLUSIONS Although TIMI grade III flow was achieved after thrombolysis, a worse STR on the surface ECG was associated with higher CFIp measured in the infarct related artery. CFIp appears to reflect the degree of microvascular obstruction by quantifying impedance of the microvasculature.