ABSTRACT
BACKGROUND: Postural tachycardia syndrome (POTS) is a complex syndrome of orthostatic intolerance that significantly affects quality of life. The relationship between functional capacity, quality of life, and age remains poorly understood in this patient population. The purpose of this cross-sectional study was to assess the clinical and exercise characteristics of patients with POTS who underwent exercise stress testing as part of cardiac rehabilitation, and to evaluate the relationships between functional capacity with age and sex, as well as the relationship between functional capacity and quality of life. METHODS: We included 255 consecutive adult patients with the diagnosis of POTS, by tilt table testing, who underwent exercise stress testing between 2012 and 2017. Clinical and stress test data were obtained from electronic medical records. RESULTS: Of the 255 patients, 232 (91%) were women, with median age 33.5 years. Prevalence of traditional CAD risk factors was low (2% diabetes, 13% hypertension, 7% hyperlipidemia, and 26% smoking history). Mean resting BP was 114 ± 13 mmHg systolic, resting HR was 76 ± 13 bpm, METs achieved 9.2 ± 2.2, and 1 min HR recovery 32 ± 17 bpm. 113 patients (44%) had abnormal functional capacity for age and sex. When analyzed by age groups, younger POTS patients had increasingly lower than expected functional capacity (compared to predicted normals) than did older patients (ANOVA P = 0.0017). The SF-36 physical component of patients with abnormal functional capacity was significantly lower than those with normal functional capacity. (p = 0.006). CONCLUSIONS: In this large cohort, patients with POTS were predominantly female (91%) and relatively young. The novel findings are that younger patients with POTS were more likely to have lower-than-average functional capacity for their age and sex compared to older patients, and that abnormal functional capacity was associated with lower quality of life by SF-36 physical component.
ABSTRACT
This study tested the hypothesis that prolonged QRS duration independently predicts long-term mortality in patients who underwent risk stratification and treatment for ventricular arrhythmias. Patients who underwent risk stratification by electrophysiologic study were identified. Electrophysiologic study results were defined as positive if sustained monomorphic ventricular tachycardia was induced. Mortality was the primary end point. Of 915 patients studied, mean left ventricular (LV) ejection fraction (EF) was 35.3 +/- 15.7%, 608 (66.4%) had coronary artery disease, 233 (25.5%) had positive electrophysiologic study findings, 298 (32.6%) received implantable cardioverter-defibrillators, and 174 (19%) died (mean follow-up 35.0 +/- 15.0 months). Cox regression analysis identified older age, coronary artery disease, digoxin use, absence of beta blockers, lower LVEF, and prolonged QRS duration to be independent predictors of mortality. QRS duration > or =130 ms, present in 33.6% of patients, was associated with a twofold increase in mortality (hazard ratio 2.1, 95% confidence interval 1.5 to 2.8; p <0.0001). For every 10 ms increase in QRS duration, mortality rate increased 10%. In a subgroup of patients with coronary artery disease and LVEF < or =30%, prolonged QRS duration remained an independent predictor of mortality (hazard ratio 2.6, 95% confidence interval 1.6 to 4.2; p <0.0001). Thus, prolonged QRS duration is a strong independent marker of long-term mortality in patients who undergo risk stratification for ventricular arrhythmias. Whether QRS duration represents only a marker for mortality or if modification of this factor using resynchronization therapies will impact mortality merits further study.
