Left ventricular hypertrophy (LVH), detected by standard 12-lead electrocardiogram (ECG) or echocardiography, is a cardinal manifestation of preclinical organ damage related to hypertension, and is a strong predictor of cardiovascular morbidity and mortality in several clinical settings . Regression of ECG or echocardiographic LVH has been shown to occur during long-term effective antihypertensive treatment, and to drive a variety of beneficial effects on left ventricular function, myocardial tissue network, coronary reserve and arrhythmias, thus resulting in an improved cardiovascular prognosis . An ECG is generally considered as the first and mandatory investigation that should be carried out in each hypertensive individual, to detect LVH, ischaemia, conduction abnormalities, left atrial dilatation and arrhythmias — particularly atrial fibrillation; its sensitivity to detect LVH is usually considered to be low (30–50%), while its specificity is high (90%) .
The QRS voltage increases with both thickening of the wall (pressure overload) and dilatation of the chamber (volume overload) of the left ventricle. The 2009 American Heart Association/American College Cardiology Foundation/Heart Rhythm Society listed as many as 35 ECG-LVH criteria based on the following: limb lead voltage; precordial lead voltage; combination of limb and precordial voltage; combinations of voltage and non-voltage criteria; and specific criteria for patients with left anterior fascicular block and right bundle branch block . More practically, recent European guidelines on hypertension highlighted four indexes: the Sokolow-Lyon index (SV1 + RV5 > 3.5 mV); the modified Sokolow-Lyon index (largest S-wave + largest R-wave > 3.5 mV); R wave in aVL lead (RaVL) > 1.1 mV; and Cornell voltage QRS duration product (> 244 mV·ms) . Among these four indexes, the Sokolow-Lyon index is most widely used by physicians, although its sensitivity is particularly low (around 30%) and no correlation has been observed with left ventricular mass index (LVMI) in obese patients . By comparison, the Cornell voltage (RaVL + SV3) and its product (Cornell voltage·QRS duration) have demonstrated better diagnostic value, but their use is compounded by the need for specific sex correction . Finally, the RaVL voltage, a component of the Cornell index, is a simple index of LVH that is not currently widely used . Recent studies have demonstrated many advantages of this last index, including its good performance in detecting LVH , which supports its revival.
RaVL is a limb voltage, well aligned with the depolarization axis of the left ventricle. Generally, RaVL increases when the heart is horizontal — an anatomical position frequently present in old and obese patients — or in the presence of LVH or left ventricle enlargement . Yet, RaVL appears to be correlated with LVMI assessed by magnetic resonance imaging (MRI), even after adjustment for age and body mass index .
The first strength of the RaVL index (which probably contributes to its good performance) is its better inter-reader reproducibility and lower variability between two successive ECGs compared with SV3, the Sokolow-Lyon index and the Cornell index . These features probably result from the fact that RaVL does not require thoracic leads, which is undoubtedly a source of variability, particularly in women.
The second interesting feature of RaVL is its univocal threshold at 1.0 mV to detect LVH, recently demonstrated in comparison with cardiac MRI . This cut-off was observed independent of sex, body mass index, previous myocardial infarction, ethnicity and conduction disorder. Using this threshold, more than 80% of patients without myocardial infarction were correctly classified according to their LVH status. Interestingly for an ECG LVH index, RaVL also had good sensibility to rule out LVH below 0.5 mV . The grey zone, between 0.5 and 1.0 mV may be an indication to perform transthoracic echocardiography (TTE) to refine the classification of these patients . Of note, several studies that previously tested RaVL in comparison with TTE reported a lower cut-off value at 0.6 mV most of the time . This lower threshold was associated with a better sensitivity but a lower specificity.
The third strength of RaVL is its prognostic value in hypertensive patients, which was recently analyzed in three studies . In 2009, Verdecchia et al. demonstrated the independent prognostic value of RaVL in the prediction of cardiovascular events in a cohort of hypertensive patients without ECG LVH (typical strain or Cornell voltage) . The optimal prognostic threshold was defined at 5.7 mm. A few years later, these data were confirmed in a Bordeaux cohort . With an optimal threshold of 4.0 mm, RaVL predicted cardiovascular events better than the Sokolow-Lyon and Cornell indexes. Another analysis in the OLD-HTA Lyon cohort demonstrated the same trend. RaVL was independently associated with cardiovascular and all-cause mortality, with optimal cut-offs at 6.0 and 8.0 mm, respectively . After excluding, in turn, patients with a positive Sokolow-Lyon index, Cornell voltage or Cornell product, the results remained statistically significant, meaning that RaVL was still able to pick up high-risk patients when other classical and more sophisticated indices failed.
For an integrative view, Table 1 summarizes different cut RaVL cut-offs for predicting LVH and cardiovascular events. The choice of a high threshold > 1.0 mm is related to a specificity of 90% to detect LVH and also to predict cardiovascular events. However, we observed this situation in only 10% of hypertensive patients. On the contrary, a lower threshold < 0.6 mm can be chosen to rule out patients at low risk. Between these two cut-offs, physicians probably need additional imaging methods to correctly stratify the risk of the remaining patients.
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