Can fragmented QRS help in risk-stratifying patients with coronary artery disease and a relatively preserved ejection fraction?

Abstract

For decades it has been a nightmare to identify the myocardial pathophysiology in patients with preserved left ventricular (LV) function despite the presence of coronary artery disease (CAD) or cardiomyopathy such as amyloidosis. Neither 12-lead electrocardiogram (ECG) nor routine echocardiography was usually very helpful in risk stratification of these patients who are at a low, but definite, risk for adverse cardiac events. The LV function measured by echocardiography and other common imaging modalities can provide the number values of LV volume ratio of systole and diastole, which is defined as ejection fraction (EF). These modalities have a major limitation in identifying the underlying myocardial dysfunction quantitatively or qualitatively in patients with preserved EF. With the advent of echocardiographic tissue Doppler imaging (TDI), diastolic dysfunction measurement is possible. Nevertheless, TDI can estimate strain only along the ultrasound beam and cannot reliably measure strain in the azimuth or perpendicular plane. Recently, the 2-dimensional (2D)–strain imaging has been developed and validated in measuring the LV dysfunction. In speckle-tracking 2D-strain echocardiographic imaging, the quantification of LV function has moved beyond the simple EF measurements. In patients with chronic ischemic LV dysfunction, a combined assessment of long-axis and short-axis functions by using 2Dstrain imaging is useful in identifying the transmural extent of myocardial infarction (MI). The value of these measurements may be more when other routine parameters do not help to identify underlying pathophysiology, especially in patients with mildly reduced or normal EF. The abnormal values of the 3 components of LV deformation (longitudinal, circumferential, and radial strains) and strain rate measurements have been shown to be sensitive indicators for subclinical myocardial diseases related to arterial hyperten-