Electrocardiography for Assessment of Hypertensive Heart Disease: A New Role for an Old Tool

Abstract

Left ventricular (LV) hypertrophy (LVH), detected either by electrocardiography (ECG) or echocardiography (ECHO), has long been recognized as a powerful predictor of serious cardiovascular (CV) sequelae. A very large and highly consistent body of evidence indicates that LVH is not only an adaptation to increased hemodynamic load in hypertension, but is also independently associated with an enhanced risk for myocardial infarction, cardiac sudden death, congestive heart failure, and stroke in the general population, as well as in patients with systemic hypertension, coronary heart disease, chronic kidney disease, and atrial fibrillation. Intriguingly, the cumulative incidence of cardiovascular events increases progressively with increasing LV mass (LVM), without evidence of any threshold separating the postulated “compensatory” from “pathological” LVH. In other words, patients with LVM in the upper-normal range already have increased risk for CV events. Moreover, various studies suggest that LVH reversal is beneficial beyond blood pressure (BP) reduction and treatment by demonstrating that CV events occur in a higher proportion of individuals in whom LVH progresses rather than regresses. There are several determinants for the development of LVH. Hemodynamic factors such as BP, large artery structure and stiffness, and volume load are important. In addition, nonhemodynamic mechanisms such as trophic factors mediated by the sympathetic nervous system, the renin-angiotensin-aldosterone system, and other neurohormonal mediators play an important role in the development of LVH. ECHO is more sensitive than ECG in diagnosing LVH and may help in the more precise stratification of overall risk and in the determination of therapy for hypertensive patients. Furthermore, ECHO measurement of LV cavity size and of myocardial relative wall thickness allows the assessment of LV geometry. The traditional classification of LV geometry in hypertensive heart disease comprised the condition of normal LVM and geometry and three abnormal LV geometric patterns: concentric LV remodeling, eccentric LVH, and concentric LVH. These LV geometric patterns have been associated with different demographic and clinical characteristics including age, sex, metabolic factors, BP levels, LV systolic and diastolic function, hemodynamic profile, extracardiac target organ damage, and CV morbidity and mortality. In particular, it has been reported that concentric LVH, connoting severe pressure overload, is associated with worse outcome than eccentric LVH or concentric remodeling. However, whether abnormal LV geometric patterns carry prognostic information beyond that provided by LV mass remains uncertain. More recently, the investigators of the Dallas Heart Study (DHS) refined this classification of hypertensive LV geometric abnormalities by introducing the concept that LVH could exist in dilated or nondilated forms, adding concentric dilated and nondilated as well as eccentric dilated and nondilated subtypes. The authors of the DHS suggested that eccentric LVH with no dilatation appeared to provide a lower risk for coronary artery disease and myocardial function impairment than in the remaining three groups of cardiac hypertrophy. However, this cross-sectional study did not present results on outcome, and the subsequent prospective investigations yielded conflicting results regarding the prognostic role of these new subtypes of LV geometric abnormalities. Nevertheless, the correct indication for ECHO in hypertensive patients is still a matter of debate. Indeed, advocating ECHO for the assessment of LVH in all hypertensive individuals would have enormous cost implications, as a result of the high number of patients. This imaging modality is more time-consuming than ECG and requires considerable skill to perform. Even though more accurate and sophisticated modalities to diagnose LVH exist, such as ECHO, computerized tomography, magnetic resonance, and, more recently, three-dimensional ECHO, ECG remains the first-choice technique to diagnose LVH in patients with hypertension because it is widely available, easy to perform, specific, inexpensive, reproducible, and of established prognostic value. ECG can also be used to detect patterns of ventricular overload or “strain” (known to indicate more severe risk), ischemia, conduction defects, and arrhythmias. Current guidelines for the management of hypertension strongly recommend ECG as the only examination to be performed in all hypertensive patients for detection of LVH. Even if ECG assessment of LVH has been incorporated among standard tests in hypertension guidelines, a recent Italian survey showed that such a recommendation is largely ignored in current clinical practice. Indeed, in this survey, <40% of the study sample had Address for correspondence: Giuseppe Mul e’, MD, Via Monte San Calogero, 29 90146 Palermo, Italy E-mail: giuseppe.mule@unipa.it