The significance of exercise-induced Q waves

doi:10.1016/0002-9343(79)90793-9

The American Journal of Medicine

Volume 67, Issue 3, September 1979, Pages 454-459

https://doi.org/10.1016/0002-9343(79)90793-9 Get rights and content

Abstract

The significance of transient exercise-induced Q waves present during treadmill testing was prospectively evaluated and correlated with the findings at cardiac catheterization. Exercise-induced Q waves were present in 14 of 560 patients (2.5 per cent) undergoing treadmill exercise testing. Thirteen patients had Q waves in leads V₁ through V₃ and one patient had Q waves in leads II, III and aVF. Ten patients underwent cardiac catheterization; six did not have coronary artery disease as determined by angiography. Two patients had a documented anterior myocardial infarction and did not undergo cardiac catheterization. Exercise myocardial perfusion imaging was performed in 10 patients. Six patients without coronary artery disease had no evidence of exercise perfusion defects. In the four patients with coronary artery disease, three patients had an abnormal resting perfusion study without change with exercise and one patient had a new exercise myocardial perfusion defect. We conclude that exercise-induced transient Q waves are not diagnostic of underlying coronary disease. In patients without coronary artery disease the mechanism of exercise-induced Q waves is as yet unclear. In patients with coronary artery disease, the mechanism may also be undefined or secondary to myocardial ischemia.

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Cited by (14)

QRS complex and ST segment manifestations of ventricular ischemia: The effect of regional slowing of ventricular activation
2013, Journal of Electrocardiology
Citation Excerpt :
Anteroseptal slowing of ventricular activation led to Q waves in aVL, and slowing in inferior location to Q waves in III and aVF. While Q waves are expected in myocardial necrosis, transient Q waves have been observed also in patients with Prinzmetal’s angina,22,23 or during a treadmill test.24,25 It is possible that slowed ventricular activation due to transient regional ischemia could be considered in these cases.
Reduction or interruption of the blood supply to myocardium due to occlusion of coronary artery and consequent ischemia leads to changes of electrogenesis: changes in morphology and duration of action potentials and slowing of conduction velocity in the affected area. In this study we simulated the effects of localized changes in depolarization sequence on the QRS and ST segment patterns, using computer modeling.
The model defines the geometry of cardiac ventricles analytically as parts of ellipsoids and allows changing the velocity of impulse propagation in the myocardium. An intramural electrically inactive area encircled by a transmural area with slowed impulse propagation velocity was introduced in anteroseptal and inferior locations. The effects on the QRS complex and the ST segment of the 12-lead electrocardiogram are presented.
The intramural electrically inactive area caused QRS changes typical for corresponding locations of a myocardial infarction observed in patients, which were further considerably modified by slowed impulse propagation velocity in the surrounding area. Additionally, areas of slowed impulse propagation velocity led to ST segment deviations in the “reciprocal” leads, shifting the ST segment towards the affected areas.
Using computer modeling we showed that the localized alteration of impulse propagation not only modified the QRS complex, but produced also changes in the ST segment consistent with changes which are usually interpreted as the effect of “injury current”.
Transient alterations of the QRS complex and ST segment during percutaneous transluminal balloon angioplasty of the left anterior descending coronary artery
1988, The American Journal of Cardiology
Using continuous 3-lead electrocardiographic (ECG) recordings in 19 patients undergoing elective percutaneous transluminal coronary artery angioplasty (PTCA) of the left anterior descending (LAD) artery, this study described the dynamic changes of the ST segment and the R- and S-wave amplitudes that occur during transient myocardial ischemia. The waveforms from lead V₂ were quantified at 10-second intervals during the length of the balloon inflation that produced the greatest extent of ST-segment deviation. The simultaneous changes that occurred in leads a VF and V₅ were also observed, but not quantified. Measurements of R- and S-wave amplitudes were performed during maximal ischemia from both the PR- and the J-ST-segment baselines to determine which of these most nearly maintained its control position during ischemia. The results indicate that the R-wave amplitude is best determined from the PR-segment baseline (p = 0.0007), while the S wave is best determined from the J-ST-segment baseline (p = 0.03). However, only a portion of the QRS changes observed during PTCA could be accounted for by the baseline shift. There were additional QRS changes during ischemia in 11 of the patients (58%) suggestive of conduction disturbances in 3 endocardial sites: left septal, right septal and left anterosuperior. It is hypothesized that these changes may represent ischemia-induced delay in conduction (“periischemic block”) previously thought to occur only with myocardial infarction.
Transient appearance of the ECG pattern of acute transmural anterior myocardial infarction during exercise stress testing
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Significance of transient electrocardiographic Q waves in coronary artery disease
1987, Cardiology Clinics
Transient Q waves in the absence of myocardial infarction mayoccur in a variety of circumstances in patients with coronary artery disease. Barring an intraventricular conduction disorder, transient Q waves usually reflect intense but reversible myocardial ischemia, requiring aggressive therapy to salvage myocardium in jeopardy. Q waves may also disappear months or years after a Q-wave myocardial infarction but rarely in the acute or subacute phase. Transient Q waves have assumed greater importance because of the current therapy of myocardial infarction and ischemia with thrombolytic agents, angioplasty, and coronary bypass surgery.
Transient “pathological” Q-waves occurring during exercise testing: Assessment of their clinical significance in a presentation of a series of patients
1987, Journal of Electrocardiology
Exercise-induced Q-waves were encountered in four Caucasian males presenting to the Cardiac Clinic, Tygerberg Hospital, with chest pain suggestive of angina pectoris. This phenomenon occurred in four out of a total of 1943 patients undergoing treadmill stress testing (Bruce Protocol) during a two-year period, giving an incidence of 0.21 percent of this ECG response. Two of the four patients (cases 1 and 2) were documented to have coronary atherosclerosis by selective coronary arteriography. One of these patients may well have been experiencing coronary vasospasm. One of the remaining two patients was a teenager whose exercise response was probably normal, whilst the last patient could have had ischemic heart disease (IHD).
This most interesting and rare response to exercise (stress) testing is discussed, emphasis being placed on its incidence, mechanism and clinical significance in IHD and other conditions in clinical practice. Awareness of the occasional transient nature of “pathological” Q-waves, whether these occur at rest or during exercise, has an important bearing on such acute therapeutic interventions as intracoronary thrombolysis and percutaneous transluminal coronary angioplasty.
Transient Q waves during exercise in hypertrophic cardiomyopathy
1985, The American Journal of Cardiology

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^☆: This study was supported in part by the Southeastern Pennsylvania Heart Association.

¹: From the William Likoff Cardiovascular Institute, Hahnemann Medical College and Hospital, 230 North Broad Street, Philadelphia, Pennsylvania.

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Clinical studyThe significance of exercise-induced Q waves☆

Abstract

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Clinical study
The significance of exercise-induced Q waves☆