Exercise-induced QRS amplitude changes in patients with isolated myocardial bridging: a marker of myocardial ischemia
Muhsin Turkmen1, Irfan Barutcu, Ali Metin Esen
1Kosuyolu Heart Education and Research Hospital Department of Cardiology, Istanbul, Turkey.
Insights
Myocardial bridging (MB) can cause exercise-induced ischemia, leading to altered QRS scores. Patients with MB show different exercise QRS scores compared to healthy individuals and those with coronary artery disease (CAD).
Area of Science:
- Cardiology
- Diagnostic Imaging
- Exercise Physiology
Background:
- Myocardial bridging (MB) is often an incidental finding, but emerging evidence links it to ischemic events.
- Understanding the functional impact of MB, particularly during stress, is crucial for accurate diagnosis and risk stratification.
Purpose of the Study:
- To evaluate exercise-induced QRS changes in patients with isolated MB.
- To compare these changes with those observed in patients with coronary artery disease (CAD) and healthy controls.
Main Methods:
- Seventeen patients with MB, 16 with LAD stenosis (CAD), and 14 healthy subjects underwent treadmill exercise testing (Bruce protocol).
- QRS wave amplitudes in leads aVF and V5 were measured pre- and post-exercise.
- The Athens QRS score was calculated to quantify exercise-induced changes.
Main Results:
- Patients with MB exhibited a higher ST-segment depression ratio than healthy subjects but lower than CAD patients.
- The exercise Athens QRS score was significantly lower in MB patients compared to healthy controls (2.9 vs. 6.5) but higher than in CAD patients (2.9 vs. 2.6).
- These findings suggest exercise-induced ischemia in the territory supplied by the bridged artery.
Conclusions:
- Exercise-induced QRS changes, assessed by the Athens QRS score, can help differentiate MB from normal coronary flow and CAD.
- MB patients demonstrate a unique pattern of ischemic response during exercise, potentially indicating subclinical myocardial ischemia.
Abstract:
Myocardial bridging (MB) of coronary arteries has been considered as an incidental angio-graphic finding; however, several reports suggest its association with angina pectoris, myocardial ischemia, and even infarction. In this study the authors aimed to assess exercise-induced QRS changes in patients with isolated MB and to compare those with coronary artery disease (CAD) and healthy subjects. The study population consisted of 17 patients with angiographically proven MB (group 1), 16 patients with left anterior descending (LAD) artery stenosis (group 2), and 14 healthy subjects (group 3). Each subject underwent treadmill exercise testing according to Bruce protocol. In each subject amplitude of the Q, R, and S waves in leads aVF and V(5) was measured manually before and immediately after exercise. The Athens QRS score was calculated by subtracting the Q-, R-, and S-wave differences in leads aVF and V(5). Baseline characteristics of each group were similar. There was no difference among the groups with respect to exercise testing parameters (peak heart rate, blood pressure, test duration, etc). In group 1, ST-segment depression ratio was found to be higher than that of group 3 but lower than that of group 2. In group 1, exercise QRS score was found to be lower than that of group 3 while it was higher than that of group 2 (2.9 +/- 2.3 vs 6.5 +/- 3.2 p = 0.001 and 2.9 +/- 2.3 vs 2.6 +/- 2.4 p = 0.001, respectively). In patients with MB exercise, QRS score was significantly lower than in those with normal coronary flow while it was higher in those with CAD. This may result from exercise-induced ischemia at the area perfused by the bridged artery.
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