Poor R-Wave Progression and Long-Term Outcomes in the Multi-Ethnic Study of Atherosclerosis (MESA)

In a large, multi-ethnic cohort of adults without baseline coronary artery disease, poor R-wave progression on an ECG was not independently associated with cardiovascular death or major adverse cardiovascular events, and its borderline association with all-cause mortality was largely attenuated after adjusting for smoking and emphysema.

The Gist

For decades, doctors have been taught that a specific pattern on an electrocardiogram (ECG) called "Poor R-Wave Progression" (PRWP) might be a sign of previous heart damage, specifically in the front part of the heart. This paper investigates whether that assumption is actually correct by studying a large group of people from the Multi-Ethnic Study of Atherosclerosis (MESA) who did not have known heart disease at the start of the study.

The researchers looked at over 6,000 participants. They compared ECGs taken at the beginning of the study to those taken about 10 years later. They also looked at advanced heart imaging (CMR), blood tests, and lung health to see what was actually causing this electrical pattern.

The study reached three main conclusions:

First, the PRWP pattern is not a stable trait. While the actual voltage measurements remained somewhat consistent, whether a person met the strict "yes or no" definition for PRWP changed significantly over a decade. About half of the people who had the pattern at the start no longer had it 10 years later, and many others developed it for the first time.

Second, the pattern does not seem to be caused by heart damage. The researchers found no link between PRWP and actual scarring on the heart, changes in the size of the right side of the heart, or markers of heart failure in the blood. Instead, the pattern was strongly linked to lung health and body shape. Specifically, people with emphysema, smokers, and people with higher BMI or larger waist circumferences were much more likely to show this pattern. This suggests that the electrical signal is being muffled or altered by the lungs and the chest wall rather than by the heart muscle itself.

Third, the pattern does not predict future health problems. When the researchers accounted for smoking and lung disease, PRWP was not an independent predictor of death or major cardiovascular events like heart attacks or strokes.

In short, the paper suggests that in people without existing heart disease, this ECG pattern is likely an electrical reflection of a person's lung health and chest anatomy rather than a warning sign of heart injury. The authors conclude that isolated PRWP should not necessarily trigger expensive or invasive cardiac testing, and that looking into a patient's pulmonary health might be a more useful approach.

Technical Summary

Technical Summary: Poor R-Wave Progression in MESA

Problem Statement

For decades, Poor R-Wave Progression (PRWP) on a 12-lead ECG has been clinically interpreted as a potential marker of prior anterior myocardial injury (scarring). However, the scientific basis for this interpretation is weak, relying on retrospective studies with significant selection bias. While some recent studies have suggested PRWP as a prognostic marker for mortality, these cohorts often included patients with pre-existing coronary artery disease (CAD). Consequently, it remains unknown whether isolated PRWP in a healthy (CAD-free) population is a stable physiological trait, a marker of myocardial substrate (like fibrosis), or merely a byproduct of non-cardiac factors such as pulmonary disease or thoracic anatomy.

Methodology

The study utilized data from the Multi-Ethnic Study of Atherosclerosis (MESA), a large, prospective, community-based cohort.

• Cohort: 6,323 participants free of clinical cardiovascular disease at baseline.
• Data Points:
  • ECG: Standardized 12-lead ECGs at baseline (Exam 1, 2000–02) and after a median of 10 years (Exam 5, 2010–12).
  • Definition of PRWP: R-wave amplitude $\leq 3$ mm in lead V3, with $RV3 > RV2$.
  • Mechanistic Substrates: Cardiac Magnetic Resonance (CMR) for right ventricular (RV) volumes/function, high-sensitivity troponin T, NT-proBNP, and polysomnography (for sleep apnea).
  • Covariates: Self-reported emphysema, smoking status, BMI, and waist circumference.
• Statistical Approach:
  • Stability: Cohen’s $\kappa$ for binary agreement and Intraclass Correlation Coefficient (ICC) for continuous R-V3 amplitude.
  • Outcomes: Cox proportional-hazards models and Fine–Gray models to assess long-term mortality (all-cause, cardiovascular, and MACE) over a median 14-year follow-up.

Key Contributions

1. Temporal Stability Analysis: The study distinguishes between the stability of the measurement (continuous amplitude) and the diagnosis (binary classification), revealing that fixed clinical thresholds can be "brittle."
2. Mechanistic Dissection: It systematically tests the "myocardial scar" hypothesis against the "pulmonary/thoracic" hypothesis using gold-standard imaging (CMR) and biomarkers.
3. Prognostic Validation in a Clean Cohort: By using a CAD-free population, the study isolates the independent prognostic value of PRWP from the confounding effects of established heart disease.

Results

• Low Reproducibility: While continuous R-V3 amplitude was reliable (ICC = 0.73), binary PRWP agreement was poor ($\kappa = 0.344$). Only 52% of baseline PRWP cases persisted after 10 years.
• Pulmonary/Thoracic Correlation: PRWP was strongly associated with self-reported emphysema (OR 4.48) and current smoking (OR 1.77). It also correlated with increased BMI and waist circumference.
• Absence of Myocardial Substrate: PRWP showed no association with RV volumes, RV ejection fraction, or NT-proBNP. While there was a modest elevation in high-sensitivity troponin T, levels remained well below clinical thresholds for myocardial injury, and no structural correlates were found.
• Null Prognostic Value: After adjusting for smoking and emphysema, PRWP was not independently associated with all-cause mortality, cardiovascular death, or MACE. The initial borderline association with mortality disappeared in time-updated and competing-risk models.

Significance

This study provides strong evidence that isolated PRWP is not a reliable indicator of myocardial injury or cardiovascular risk in individuals without established coronary disease. Instead, it appears to be an electrical pattern driven by thoracic habitus and pulmonary changes (such as emphysema and smoking-related lung changes) that attenuate the ECG signal.

Clinical Implication: The authors suggest that clinicians should avoid unnecessary downstream cardiac workups (like echocardiography or stress testing) prompted solely by an automated "abnormal" PRWP flag in patients without other symptoms or CAD. Instead, such a finding may be more indicative of a need for pulmonary evaluation.