Electrocardiographic Markers of Subclinical Myocardial Dysfunction in Patients with Severe Obesity and Normal Ejection Fraction. The FatWest Study

Introduction: Patients with severe obesity are predisposed to left ventricular (LV) myocardial dysfunction and increased myocardial oxygen (O 2 ) demand despite preserved ejection fraction (EF). Hypothesis: To test whether electrocardiography (ECG) may be used to identify patients with severe obesity that have myocardial dysfunction despite normal EF by echocardiography. Methods: In the prospective FatWest (Bariatric Surgery on the West Coast of Norway) study, 116 severely obese patients (41±11 years, 75% women, body mass index [BMI] 41.7±4.6 kg/m 2 , 57% with hypertension, EF 61±5%) underwent 12-lead ECG and echocardiography before a Roux-en-Y gastric bypass surgery. Low LV mechanics was defined as global longitudinal strain (GLS) below the median, and high myocardial O 2 demand as LV mass-wall stress-heart rate product above the median value. ECG markers of atrial (P axis and duration) and ventricular (QRS axis and duration, T axis, QRS-T angle, time to intrinsicoid deflection (ID), and corrected QT (QTc)) de- and repolarization were analyzed. Results: Median GLS was -15.5%, and median myocardial O 2 demand 1.47 x106 g kdyne/cm 2 bpm. Patients with low GLS had longer QRS, time to ID and QTc duration, while those with high myocardial O 2 demand had increased P axis and duration (all p<0.05). In multivariate regression analyses, longer QTc was associated with lower GLS (R 2 0.24) and increased P axis with higher myocardial O 2 demand (R 2 0.21) independent of age, gender, BMI and hypertension (all p<0.05). A QTc >435ms and P axis >42° had 70% specificity in detecting low GLS and high myocardial O 2 demand (Figure). Conclusion: In severely obese patients, ECG measures of atrial activation and delayed ventricular repolarization were independently associated with low LV myocardial function and high myocardial O 2 demand. ECG screening before bariatric surgery may identify patients in whom advanced echocardiography is warranted.