High output cardiac state: evaluating the incidence, plausible etiologies and outcomes

Introduction: The high output cardiac state (HOCS) [cardiac index (CI) >4 L/min/m2 ], primarily driven by abnormally low systemic vascular resistance (SVR), is a relatively under-recognized condition. Although, majority of these patients meet criteria for heart failure (HF), their treatment should be aimed at the primary pathology, as the majority of guideline directed HF therapies can reduce SVR further.

Objectives: To characterize patients with HOCS and provide valuable insight into the condition.

Methods: Patients investigated by right heart catheterization (RHC) at the St. Boniface Hospital, Winnipeg, Canada between January 2009 and November 2021 were reviewed. Two groups of patients were included: 1) HOCS [CI >4 L/min/m²], and 2) pre-HOCS [CI between 3.8-4.0 L/min/m²]. Their medical records were reviewed to identify plausible etiologies, relevant investigations, and outcomes.

Results: 177/2950 (6 %) patients met criteria for inclusion: 144/177 (81 %) with HOCS [mean age 51 years (range 19 - 82); 67/144 (47 %) female] and 33/177 (19 %) with pre-HOCS [mean age 55 years (range 30 - 83); 6/33 (18 %) female]. The most common plausible etiologies for the HOCS included anemia (36 %), obesity (34 %), cirrhosis (17 %), and lung disease (32 %). Trans-thoracic echocardiography and magnetic resonance imaging findings were non-specific and predominantly described preserved left ventricular ejection fraction, and pulmonary hypertension. The population experienced high rates of hospitalization, and significantly high mortality [36/144 (25 %) of HOCS at a median follow-up of 31.5 months, and 13/33 (39 %) of pre-HOCS at a median follow-up of 17 months].

Conclusions: HOCS is not an uncommon condition and is associated with high mortality. Current HF guideline should incorporate such evaluation into the diagnostic criteria.