An indicator of sudden cardiac death during brief coronary occlusion: electrocardiogram QT time and the role of collaterals

The coronary collateral circulation has a beneficial role regarding all-cause and cardiac mortality. Hitherto, the underlying mechanism has not been clarified. The aim of this prospective study was to assess the effect of the coronary collateral circulation on electrocardiogram (ECG) QTc time change during short-term myocardial ischaemia. A total of 150 patients (mean age 63 +/- 11 years, 38 women) were prospectively included in this study. An ECG was recorded at baseline and during a standardized 1 min coronary balloon occlusion. QT interval was measured before, during, and after balloon occlusion and was corrected for heart rate (QTc). Simultaneously obtained collateral flow index (CFI), expressing collateral flow relative to normal anterograde flow, was determined based on intracoronary pressure measurements. During occlusion of the left anterior descending coronary artery mean QTc interval increased from 422 +/- 33 to 439 +/- 36 ms (P < 0.001), left circumflex occlusion led to an increase from 414 +/- 32 to 427 +/- 27 ms (P < 0.001). QTc was not influenced by occlusion of the right coronary artery (RCA) (417 +/- 35 and 415 +/- 34 ms, respectively; P = 0.863). QTc change during occlusion of the left coronary artery was inversely correlated with CFI (R(2) = 0.122, P = 0.0002). Myocardial ischaemia leads to QT prolongation during a controlled 1 min occlusion of the left, but not the RCA. QT prolongation is inversely related to collateral function indicating a protective mechanism of human coronary collaterals against cardiac death.