P-wave duration as a non-invasive biomarker for left atrial remodeling in healthy Shih Tzu

Degenerative mitral valve disease (DMVD) is the most prevalent canine cardiac condition, with left atrial enlargement (LAE) being a critical predictor of progression to congestive heart failure (CHF) and arrhythmogenesis. Identifying accessible, non-invasive markers for preclinical according with the American College of Veterinary Internal Medicine - ACVIM (ACVIM Stage A) remodeling is paramount for timely risk stratification. This study investigated the relationship between electrocardiographic (ECG) P-wave duration and key echocardiographic metrics: indexed left atrial end-systolic volume (LAESV IDX), LA/Ao ratio, and normalized Left Ventricular internal diameter (LVIDDn), in a tightly controlled cohort of 22 Shih Tzu dogs (ACVIM Stage A). The mean P-wave duration was 39.55±3.63 ms. Significant positive correlations were found with all remodeling parameters (p<0.05), being the strongest with LAESV IDX (r = 0.61; p=0.002). Linear regression established LAESV IDX as the most robust predictor of P-wave duration (adjusted R²=0.342; p=0.002). Reference thresholds were derived based on ACVIM criteria and sample P95 (LAESV IDX: 44 ms; LA/Ao: 49ms). A transition zone (44-49 ms) suggestive of incipient LAE is proposed. P-wave duration is concluded to be a sensitive, readily available, non-invasive biomarker of preclinical cardiac remodeling in Shih Tzu dogs, enhancing tools for early risk stratification.