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Symptomatic, electrocardiographic, metabolic, and hemodynamic alterations during pacing-induced myocardial ischemia
Insights
Atrial pacing can reveal coronary artery disease (CAD) by inducing myocardial ischemia. While ECG changes and lactate production are specific, they are insensitive markers. Chest pain is nonspecific in CAD patients and healthy individuals during pacing.
Area of Science:
- Cardiology
- Diagnostic Medicine
- Physiology
Background:
- Atrial pacing is utilized to evaluate the physiological effects of coronary artery disease (CAD).
- The diagnostic accuracy of various markers for pacing-induced myocardial ischemia remains unclear.
Purpose of the Study:
- To determine the sensitivity and specificity of different variables as markers of pacing-induced myocardial ischemia in patients with and without CAD.
Main Methods:
- Incremental atrial pacing was performed in 28 patients (10 without CAD, 18 with CAD).
- Measurements included left ventricular ejection fraction (LVEF), left ventricular end-diastolic pressure, lactate levels, electrocardiographic changes, and chest pain occurrence.
Main Results:
- In patients with CAD, atrial pacing induced myocardial ischemia, evidenced by decreased LVEF and new wall motion abnormalities.
- Electrocardiographic changes and lactate production were specific but insensitive markers of ischemia.
- Chest pain occurred in 67% of CAD patients and 40% of controls, indicating its nonspecificity.
Conclusions:
- Electrocardiographic, metabolic, and hemodynamic markers of pacing-induced ischemia are specific but lack sensitivity.
- Chest pain during atrial pacing is not a reliable indicator of myocardial ischemia in patients with or without CAD.
Abstract:
Atrial pacing has been used to assess the physiologic impact of coronary artery disease (CAD). Several variables have served as markers of pacing-induced myocardial ischemia, but their specificities and sensitivities are unknown. Accordingly, in 28 patients, incremental atrial pacing was performed. Of the 28, 10 had no CAD. The left ventricular ejection fraction (LVEF) (by gated equilibrium blood pool scintigraphy) increased in this group (0.60 +/- 0.11 [mean +/- standard deviation] before pacing to 0.67 +/- 0.13 at peak-pacing, p = 0.002). In no patient did left ventricular end-diastolic pressure increase by greater than 5 mm Hg. No patient had lactate production, and 2 (20%) had electrocardiographic S-T segment depression greater than or equal to 0.1 mV. Four (40%) had chest pain with atrial pacing. In the remaining 18 patients with CAD, atrial pacing caused a decrease in LVEF greater than or equal to 0.05 (0.46 +/- 0.10 to 0.33 +/- 0.09, p less than 0.001) and new segmental wall motion abnormalities in all, indicating pacing-induced myocardial ischemia. Only 8 (44%) had an increase in left ventricular end-diastolic pressure of greater than 5 mm Hg, and only 9 (50%) had lactate production. Ten (56%) had ischemic electrocardiographic changes, and 12 (67%) had chest pain. Thus, the electrocardiographic, metabolic, and hemodynamic alterations that may accompany pacing-induced ischemia are specific but relatively insensitive markers of ischemia. In contrast, chest pain during atrial pacing is a nonspecific occurrence, appearing with similar frequency in normal subjects and patients with CAD and pacing-induced ischemia.