What is the clinical evidence from this study?

Study design: Cohort. Population: Coronary artery disease (n=342). Intervention: Top quartile of P wave area vs. Remainder of the population. Primary outcome: Incident atrial fibrillation or flutter (HR 2.6, 95% CI 1.1-5.9, p=0.02).

June 5, 2014Open Access

P Wave Area for Quantitative Electrocardiographic Assessment of Left Atrial Remodeling

JWJonathan W. WeinsaftCardiac Imaging JKJonathan KochavNewYork–Presbyterian Hospital JKJiwon KimTwitter (United States)

Key Result

Patients in the top quartile of ECG-quantified P wave area had a 2.6-fold increased risk of incident atrial fibrillation or flutter compared to the remainder of the population (HR 2.6).

Study Design

Type

Cohort (n=342)

Blinding

Blinded assessors

Multicenter

Structured PICO

Does ECG-quantified P wave area correlate with CMR-evidenced left atrial remodeling and predict atrial arrhythmic risk in patients with CAD?

Population

342 patients with coronary artery disease who underwent ECG and CMR within a 1-week interval, followed for a mean of 2.4 years to assess atrial arrhythmic risk.

Exposure

ECG-quantified P wave area (specifically in lead V1)

Comparator

CMR-evidenced left atrial (LA) area and echocardiography

Outcome

Correlation between P wave area and LA area on CMRsurrogate

ECG-quantified P wave area serves as a non-invasive index of left atrial remodeling that correlates with CMR geometry and independently predicts the risk of atrial arrhythmias.

Main Result

Hazard Ratio: 2.6 (95% CI 1.1–5.9)

p-value: p=0.02

Limitations

Left atrial size can change dynamically due to transient alterations in loading conditions between ECG and CMR acquisition.
Event rates were captured based on clinical documentation, raising the possibility that clinically silent episodes were missed.
The number of clinical endpoints was relatively low (n=25), limiting definitive conclusions regarding longitudinal risk stratification.
The study was restricted to subjects with ischemic heart disease, which may limit generalizability to other populations.

Abstract

BACKGROUND: Left atrial (LA) dilation provides a substrate for mitral regurgitation (MR) and atrial arrhythmias. ECG can screen for LA dilation but standard approaches do not assess LA geometry as a continuum, as does non-invasive imaging. This study tested ECG-quantified P wave area as an index of LA geometry. METHODS AND RESULTS: 342 patients with CAD underwent ECG and CMR within 7 (0.1±1.4) days. LA area on CMR correlated best with P wave area in ECG lead V1 (r = 0.42, p<0.001), with lesser correlations for P wave amplitude and duration. P wave area increased stepwise in relation to CMR-evidenced MR severity (p<0.001), with similar results for MR on echocardiography (performed in 86% of patients). Pulmonary arterial (PA) pressure on echo was increased by 50% among patients in the highest (45±14 mmHg) vs. the lowest (31±9 mmHg) P wave area quartile of the population. In multivariate regression, CMR and echo-specific models demonstrated P wave area to be independently associated with LA size after controlling for MR, as well as echo-evidenced PA pressure. Clinical follow-up (mean 2.4±1.9 years) demonstrated ECG and CMR to yield similar results for stratification of arrhythmic risk, with a 2.6-fold increase in risk for atrial fibrillation/flutter among patients in the top P wave area quartile of the population (CI 1.1-5.9, p = 0.02), and a 3.2-fold increase among patients in the top LA area quartile (CI 1.4-7.0, p = 0.005). CONCLUSIONS: ECG-quantified P wave area provides an index of LA remodeling that parallels CMR-evidenced LA chamber geometry, and provides similar predictive value for stratification of atrial arrhythmic risk.

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