Open AccessExercise‐induced QTc‐interval changes for predicting improvement in regional blood flow in ischemic myocardium and cardiac output after coronary angioplasty in patients with right bundle‐branch block
Author(s) -
Watanabe Takuya,
Katagiri Takashi,
Yamanaka Hideyuki,
Akutsu Yasushi,
Michihata Tetsuo,
Okazaki Osamu,
Harumi Kenichi
Publication year - 2000
Publication title -
clinical cardiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.263
H-Index - 72
eISSN - 1932-8737
pISSN - 0160-9289
DOI - 10.1002/clc.4960230511
Subject(s) - medicine , cardiology , qt interval , ischemia , angioplasty , right bundle branch block , percutaneous transluminal coronary angioplasty , blood flow , electrocardiography
Background: We have previously shown that QT‐interval changes are more useful than ST‐T changes in evaluating the severity of exercise‐induced myocardial ischemia in patients with right bundle‐branch block (RBBB). Hypothesis: The purpose of this study was to evaluate whether the improvement in regional myocardial blood flow (RMBF) in ischemic areas and cardiac output after percutaneous transluminal coronary angioplasty (PTCA) can be predicted by exercise‐induced QT‐interval changes prior to PTCA. Methods: The RMBF and cardiac output were quantified with nitrogen‐13 ammonia positron emission tomography at rest and during exercise in 20 patients with RBBB and ischemic heart disease before and 6 months after PTCA, and in 9 healthy volunteers. Results: Before PTCA, exercise‐induced prolongation by <20 ms or shortening of the Bazett‐corrected QT (QTc) interval (454 ± 38 to 451 ± 41 ms, p = NS) was observed in 13 patients (Group 1) and prolongation by ≥20 ms (429 ± 44 to 466 ± 50 ms, p < 0.002) was observed in 7 (Group 2). The number of regions of exercise‐induced ischemia was significantly greater in Group 2 than in Group 1 (4.0 ± 1.2 vs. 2.1 ± 1.2, p < 0.01). The RMBF in regions of exercise‐induced ischemia and cardiac output at rest was not significantly different between Groups 1 and 2, whereas during exercise both the parameters were significantly lower in Group 2 than in Group 1 (both p < 0.05). After successful PTCA, RMBF both at rest and during exercise improved significantly in Group 1 (0.67 ± 0.04 to 0.71 ± 0.06 ml/min/g, 0.74 ± 0.05 to 0.84 ± 0.08 ml/min/g; both p < 0.0001), but did not improve significantly in Group 2 (0.63 ± 0.05 to 0.65 ± 0.07 ml/min/g, 0.65 ± 0.04 to 0.69 ± 0.11 ml/min/g; both p = NS). Cardiac output during exercise improved significantly in Group 1 (6.4 ± 0.7 to 7.4 ± 0.9 l/min; p<0.002) but not in Group 2 (5.7 ± 0.6 to 5.9 ± 0.6 l/min; p = NS). Conclusions: Our results suggest that the marked prolongation of the QTc interval induced by pre‐PTCA exercise may predict a lack of improvement in RMBF in ischemic areas and cardiac output after PTCA in patients with RBBB and ischemic heart disease.