Prognostic Value of Microvascular Resistance at Rest in Patients With Takotsubo Syndrome

Background: Microvascular resistance (MR) is increased in takotsubo syndrome (TTS) and can be assessed by a validated pressure-wire-free tool called nonhyperemic angiography-derived index of microcirculatory resistance (NH-IMRangio). Objectives: The authors aimed to study whether the degree and extent of an altered MR in TTS patients were associated with 1-year prognosis. Methods: The authors recruited 181 consecutive patients with TTS who underwent cardiac angiography. Impaired MR was defined as an NH-IMRangio ≥25. The degree and extent of impaired MR were assessed by the value of maximum NH-IMRangio in each major coronary artery and by the number of coronary arteries with an NH-IMRangio ≥25, respectively. Major adverse cardiac events (MACE) were a composite of cardiovascular death, heart failure event, acute myocardial infarction, and hospitalization for symptomatic arrhythmias. Results: A total of 166 patients had NH-IMRangio available. The mean age was 74.8 years, and 83% were women. The rate of MACE at 1 year was 21.1%, mainly due to heart failure events that were generally mild. Kaplan-Meier curves showed higher rates of MACE in patients with higher NH-IMRangio (28.9% vs 13.3%; P = 0.019) and in those with 3 coronary arteries with increased MR compared to those with 2 or 1 affected arteries (33.3% vs 15.9% vs 9.5%; P = 0.040 and P = 0.040, respectively). After a multivariable Cox regression analysis, higher values of NH-IMRangio (HR: 3.41 [95% CI: 1.54-7.52]; P = 0.002) and the presence of 3 coronary arteries with increased MR (HR: 6.39 [95% CI: 1.46-27.87]; P = 0.014) were independent predictors of MACE in TTS patients. Conclusions: The degree and extent of an impaired MR assessed by a validated pressure-wire-free tool were independent predictors of MACE at 1-year follow-up in TTS patients.