P-wave indices in patients with pulmonary emphysema: do P-terminal force and interatrial block have confounding effects?

Abstract

IntroductionPulmonary emphysema causes several electrocardiogram changes, and one of the most common and well known is on the frontal P-wave axis. P-axis verticalization (P-axis > 60°) serves as a quasidiagnostic indicator of emphysema. The correlation of P-axis verticalization with the radiological severity of emphysema and severity of chronic obstructive lung function have been previously investigated and well described in the literature. However, the correlation of P-axis verticalization in emphysema with other P-indices like P-terminal force in V1 (Ptf), amplitude of initial positive component of P-waves in V1 (i-PV1), and interatrial block (IAB) have not been well studied. Our current study was undertaken to investigate the effects of emphysema on these P-wave indices in correlation with the verticalization of the P-vector.Materials and methodsUnselected, routinely recorded electrocardiograms of 170 hospitalized emphysema patients were studied. Significant Ptf (s-Ptf) was considered ≥40 mm.ms and was divided into two types based on the morphology of P-waves in V1: either a totally negative (−) P wave in V1 or a biphasic (+/−) P wave in V1.Resultss-Ptf correlated better with vertical P-vectors than nonvertical P-vectors (P = 0.03). s-Ptf also significantly correlated with IAB (P = 0.001); however, IAB and P-vector verticalization did not appear to have any significant correlation (P = 0.23). There was a very weak correlation between i-PV1 and frontal P-vector (r = 0.15; P = 0.047); however, no significant correlation was found between i-PV1 and P-amplitude in lead III (r = 0.07; P = 0.36).ConclusionWe conclude that increased P-tf in emphysema may be due to downward right atrial position caused by right atrial displacement, and thus the common assumption that increased P-tf implies left atrial enlargement should be made with caution in patients with emphysema. Also, the lack of strong correlation between i-PV1 and P-amplitude in lead III or vertical P-vector may suggest the predominant role of downward right atrial distortion rather than right atrial enlargement in causing vertical P-vector in emphysema.

Letter by Chhabra et al Regarding Article, “Prevalence and Prognostic Significance of Abnormal P Terminal Force in Lead V 1 of the Electrocardiogram in the General Population”

“…5 Hence, the standard V1 chest lead in patients with emphysema ultimately monitors electric forces of a much lower-situated right atrium, which probably records the atrial depolarization vector going in opposite direction from the lead V1, resulting in a predominant negative P deflection. 4 In fact, a totally negative P wave rather than a biphasic P wave were common in emphysematous patients. How did authors compute the PTF in cases with a totally negative P wave in V1 remains somewhat unclear from the current study?…”

“…In one of our previous works, we demonstrated that PTF may often be falsely increased in these patients and interpretation of left atrial enlargement in such patients based on PTF alone should be made with caution. 4 This is because emphysema causes diaphragmatic flattening because of hyperinflation and creates a downward pull on the heart/right atrium via the dense pericardial ligament. 5 Hence, the standard V1 chest lead in patients with emphysema ultimately monitors electric forces of a much lower-situated right atrium, which probably records the atrial depolarization vector going in opposite direction from the lead V1, resulting in a predominant negative P deflection.…”

Short-term repeatability of electrocardiographic P wave indices and PR interval

“…Novel indices such as P wave area have gained attention and are also predictive of AF (6, 9). Traditionally, abnormalities in P wave indices have been used to define left and right atrial enlargement (10), and screen for chronic obstructive pulmonary disease (11) and emphysema (12, 13). …”

Importance of P-wave indices in stroke

“…Thus, the presence of PTF should be accounted with respect to the presence of IAB which would provide a sound explanation for the observed increase in cardioembolic events in such patients. One caution should be exercised in the interpretation of increased PTF especially without accompanying IAB in patients with a known history of chronic obstructive lung disease or emphysema [8][9]. Patients with emphysema may exhibit an increased PTF which is often secondarily to the right atrial distortion such that lead V1 in actuality monitors the electrical forces of a much lower-situated right atrium and records the atrial depolarization forces going away from lead V1, manifesting as a negative P-deflection or an increased PTF [8][9].…”

“…One caution should be exercised in the interpretation of increased PTF especially without accompanying IAB in patients with a known history of chronic obstructive lung disease or emphysema [8][9]. Patients with emphysema may exhibit an increased PTF which is often secondarily to the right atrial distortion such that lead V1 in actuality monitors the electrical forces of a much lower-situated right atrium and records the atrial depolarization forces going away from lead V1, manifesting as a negative P-deflection or an increased PTF [8][9]. Thus, in patients with an extensive smoking history such as in the current study population (smoking prevalence = 44%), it would be valuable to account for the prevalence of COPD in relation to the PTF.…”