Impaired Exercise Capacity Despite Recovered Cardiac Function In A Patient With Stress Cardiomyopathy

HISTORY: A 73-year-old woman was diagnosed with atrial fibrillation, with a cardiac stress test showing normal left ventricular ejection fraction (LVEF) at 61% and estimated peak exercise capacity of 4.5 METS. She was prescribed an angiotensin receptor blocker and beta blocker. Eight months later, she experienced a stressful event and was hospitalized with mid-ventricular stress cardiomyopathy (Takotsubo syndrome), with a newly reduced LVEF of 35-40%. She was prescribed guideline directed medical therapy (GDMT) for heart failure (HF). Four months later, as expected, LVEF recovered to 60-65%, and GDMT for HF was discontinued. Three months later, the patient was hospitalized again after a stressor. BNP was 346 pg/mL. Echocardiography showed a mid-ventricular stress cardiomyopathy, with LVEF at 40-45%. Patient was restarted on GDMT and referred to outpatient cardiac rehabilitation (CR). Two months later (before beginning CR), an echocardiogram was repeated at rest and after peak cardiopulmonary exercise testing (CPET). PHYSICAL EXAMINATION: Irregularly irregular rhythm with no ST-segment changes. Blood pressure and pulse were within normal limits. DIFFERENTIAL DIAGNOSIS: Impaired cardiorespiratory fitness secondary to stress cardiomyopathy, non-ischemic cardiomyopathy, and/or atrial fibrillation. TEST AND RESULTS: LVEF recovered to 57%, E/e’ was normal at 8, with resting heart rate (HR) 80 and blood pressure at 104/68 mmHg. BNP increased to 544 pg/mL. ECG showed atrial fibrillation throughout testing. CPET showed VO2peak was reduced to 13.8 ml/kg/min (73% predicted; 3.7 METS), with a peak RER 1.07, elevated VE/VCO2 slope at 39.6, impaired OUES at 1.17. Peak HR was 144 bpm (98% predicted), and E/e’ 9 after peak exercise. Cardiac output was 3.0 L/min at rest and 10.3 L/min at peak exercise. FINAL WORKING DIAGNOSIS:Persistent impairment of cardiorespiratory fitness despite LVEF recovery in patients with stress cardiomyopathy (see Scally et al., Circulation 2017;137:1039). TREATMENT AND OUTCOMES:The patient completed 36 CR sessions over 4 months. After CR, LVEF was 60-65% and E/e’ 7.5. Repeat 6MWT revealed exercise capacity estimated at 3.3 METS, unchanged versus prior. Patients with stress cardiomyopathy experience a decline in cardiorespiratory fitness that can persist beyond recovery of LVEF.