Is the electrocardiogram still useful in detecting right ventricular abnormalities in patients with pulmonary hypertension when compared to echocardiography?

Abstract

In pulmonary hypertension (PH), unopposed increases in pulmonary vascular resistance will trigger right ventricular (RV) structural and functional remodeling changes that could result in RV failure, the main cause of death in patients with PH. While transthoracic echocardiography (TTE) is a widely recognized noninvasive imaging tool in the evaluation of RV abnormalities in PH; the electrocardiogram (ECG) though still obtained as part of initial PH workup suffers from limitations in sensitivity (55%) and specificity (70%). However, recent cardiac magnetic resonance data suggests that ECGs might still be useful to detect changes in RV load. Consequently, we queried our database and found a heterogeneous group of 85 patients with PH who had both ECG and TTE to determine whether any of the common ECG abnormalities known to occur in PH such as resting tachycardia, changes in the amplitude of R and S waves in precordial lead V1, and frontal axis deviation 110 degrees was useful in identifying any significant RV structural or functional abnormalities by echocardiography. The University of Cincinnati IRB approved this study. All TTE examinations were performed according to published guidelines and measurements were compared using two-tailed unpaired t-test assuming unequal variances. ECGs were read by two independent readers (Inter-rater agreement: Kappa static5 0.86 and 95% confidence interval) blinded to TTE results. P-values of less than .05 were considered to be statistically significant. All statistics were calculated in MedCalc Software bvba Version 14.12.0 (Belgium). In the population studied, patients with sinus tachycardia had significantly higher pulmonary artery systolic pressures. In the case of right axis deviation, not only patients were younger but also had higher pulmonary artery systolic pressures with worse RV systolic function. Finally, no RV echocardiographic abnormalities were abnormal with an rsR’ pattern in lead V1. The results of this small comparative study once again fail to show any significant correlation between ECG and RV abnormalities when assessed by TTE. However, before we completely discredit the utility of ECGs to assess PH patients it is important to highlight data from recent studies in both rats and humans showing that even a mild increase in RV pressure load is associated with substantial changes in myocardial electrical properties, detectable in a standard ECG recording when three-dimensional echocardiography or cardiac magnetic resonance imaging are used. Furthermore, some ECG abnormalities are known to occur more commonly in specific subgroups of PH patients. More specifically, right bundle branch block is an independent predictor of mortality in patients with systemic sclerosis while conduction abnormalities not only are common in patients with chronic obstructive pulmonary disease, but also these ECG abnormalities increase with disease severity. In conclusion, the jury is still regarding the potential value for ECG in PH, particularly with regards to anatomical and functional RV abnormalities. Therefore, continued vigilance for results of ongoing studies using more advanced imaging tools is of outmost importance before we can discard the potential utility of ECG when evaluating PH patients.