Fragmented QRS: A marker of hypertensive heart disease?

Fragmented QRS complexes (fQRS) on surface electrocardiography is defined as an rSR′ pattern in the absence of typical bundle branch block. Morphologically, it represents an altered QRS complex that has a duration <120 ms and has either an additional R wave, notching in the nadir of the S wave, or an additional R′ wave. Given that it likely reflects altered ventricular depolarization, its potential association with myocardial injury has drawn the attention of many clinicians and cardiovascular investigators. Particularly, it has been noted that it may be superior to the Q wave in identifying persons with prior myocardial injury. In a study of roughly 500 patients referred for nuclear stress test by single-photon emission computed tomography, the sensitivity and negative predictive value of fQRS for myocardial scar defined by regional perfusion abnormalities was compared with those of the Q wave. Both parameters were greater for fQRS compared with Q wave (namely 85.6% vs 36.3% and 92.7% vs 70.8%, respectively).1 One main explanation has been that Q waves regress or even disappear in patients with Q-wave infarct.2 Several studies have shown absence of Q wave in about two thirds of patients with a documented Q wave or non–Q-wave myocardial infarction (MI), indicating its limitations in detection of myocardial scar. More than 4 decades ago the first association between rSR′ pattern in left precordial leads and ventricular aneurysm was reported. Persistent fQRS associated with decreased survival after acute MI and transient fQRS has been associated with recurrent MI.3 Patients with elevated blood pressure may develop myocardial fibrosis, which can be visualized by cardiac magnetic resonance imaging. Development of myocardial fibrosis, similar to injuries caused by MI or cardiomyopathies, has been associated with increased risk of cardiac arrhythmia and, hence, increased mortality.4 In the article by Eyuboglu and colleagues, the investigators present their study of the prevalence of fQRS in patients with concealed hypertension. A total of 548 “healthy” persons without cardiac hypertrophy underwent 24-hour ambulatory blood pressure monitoring and ECG screening. Patients with echocardiographic evidence of left ventricular (LV) hypertrophy, previous MI or coronary artery bypass surgery, complete or incomplete bundle branch block or QRS duration ≥120 ms, LV ejection fraction <50%, or moderate to severe valvular disease were excluded. fQRS pattern was significantly higher in patients with hypertension and prehypertension vs those with normotension. Multivariate logistic regression analysis revealed that systolic blood pressure is an independent predictor of presence of fQRS. Using receiver operating characteristic analysis, a 147.65-mm Hg cutoff value for systolic blood pressure was found to predict the presence of fQRS on electrocardiography with a 51% sensitivity and 99% specificity. Other associated risk factors were age, diabetes mellitus, and cigarette smoking. The authors then argued that the presence of fQRS on electrocardiography may be an indicator of myocardial fibrosis and is likely associated with poor prognosis. The study has some methodological problems, which are mainly the result of the lack of access to advanced imaging technologies. Hence, the presence of cardiac fibrosis in the study participants was not examined. Also, the prevalence of cardiovascular events, ie, MI, stroke, transient ischemic attack, or development of complications such as renal failure and LV hypertrophy, between patients with and those without fQRS were not compared. The association between fQRS and hypertension, LV hypertrophy, and LV mass index has been previously reported.5, 6 The presence of fQRS on electrocardiography has also been linked to myocardial fibrosis in patients with hypertension.7 Another complication of hypertension is diastolic dysfunction and atrial fibrillation. These two conditions are often associated with atrial stiffness. The presence and number of fQRS in patients undergoing coronary artery bypass graft surgery has been shown to be an independent predictor of new-onset postoperative atrial fibrillation.8 In a prospective study of 301 patients without overt structural heart disease, the relationship between fQRS and paroxysmal atrial fibrillation was examined. Patients with fQRS were older, had larger left atria, had more cardiac hypertrophy, and more often had diabetes mellitus. A multivariate logistic regression analysis identified fQRS as an independent predictor of paroxysmal atrial fibrillation.9 In a different study of 39 patients with kidney transplant, fQRS was detected in 16 patients. A history of hypertension was associated with the presence of fQRS. Patients with fQRS had lower systolic and peak early diastolic mitral annular velocities, mitral annular plane systolic excursion, and LV ejection fraction than those without fQRS. These findings suggest that the presence of fQRS on surface electrocardiography may correlate with systolic and diastolic dysfunction of the left ventricle in patients with kidney transplant.10 The novelty of the current study is the identification of patients with concealed hypertension in the absence of LV hypertrophy. Routine electrocardiography may be helpful in identifying patients with masked hypertension and in differentiating between patients with true hypertension and those with white-coat hypertension in office visits. Future studies should be able to determine whether patients with concealed hypertension and fQRS have a different prognosis than those without it. Reduction of LV hypertrophy with calcium antagonists and β-blockers has been shown to reduce ventricular arrhythmias. It is important to investigate whether medical therapy for hypertension can result in normalization of the ECG findings, reduced ventricular arrhythmias, and/or improved prognosis in these patients. The author has no conflicts of interest to disclose.