Hypoxia Due to a Large Right to Left Interatrial Shunt with Normal Right-Sided Filling Pressures in the Setting of a Separation between the Septum Primum and Secundum: A Case Report

Hypoxia secondary to right to left interatrial shunting in the setting of normal right-sided filling pressure is an uncommon clinical presentation. We present a case of persistent hypoxia irrespective of body position in a patient with a wide separation between the septum primum and secundum, creating a tunnel channeling flow from the right to the left atrium. Hypoxia resolved instantly following closure of the defect with an Amplatzer occluder under intracardiac echocardiography guidance. Although platypnea-orthodeoxia leads to hypoxia in the setting of normal right-sided filling pressures, the finding of a coexisting wide gap between the septum primum and secundum is likely to have worsened the hypoxia making it severe irrespective of body position. Closure of the interatrial septal defect led to immediate and sustained resolution of the hypoxia.

No-Implant Interatrial Shunt for HFpEF: 6-Month Outcomes From Multicenter Pilot Feasibility Studies

BACKGROUND

Most approaches to the creation of an interatrial shunt require placement of a permanent implant to maintain patency.

OBJECTIVES

The goal of this study was to investigate the safety and efficacy of a no-implant interatrial shunt for patients with heart failure with preserved ejection fraction (HFpEF) and heart failure with mildly reduced ejection fraction (HFmrEF).

METHODS

This was a multicenter, uncontrolled study of patients with HFpEF/HFmrEF and NYHA functional class ≥II, ejection fraction >40%, and pulmonary capillary wedge pressure (PCWP) during supine exercise ≥25 mm Hg with PCWP-to-right atrial gradient ≥5 mm Hg. Follow-up was through 6 months with imaging to assess shunt durability.

RESULTS

A total of 28 patients were enrolled: mean age was 68 ± 9 years, and 68% were female. Baseline resting and peak exercise PCWP were 19 ± 7 mm Hg and 40 ± 11 mm Hg, respectively. All procedures displayed technical success with confirmation of left-to-right flow (shunt diameter 7.1 ± 0.9 mm). At 1 month, peak exercise PCWP decreased 5.4 ± 9.6 mm Hg (P = 0.011) with no change in right atrial pressure. There were no serious device or procedure-related adverse events through 6 months. Mean 6-minute walk distance increased 101 ± 71 meters (P < 0.001); Kansas City Cardiomyopathy Questionnaire Overall Summary Score increased 26 ± 19 points (P < 0.001); N-terminal pro-B-type natriuretic peptide decreased 372 ± 857 pg/mL (P = 0.018); and shunt patency was confirmed with unchanged diameter.

CONCLUSIONS

In these feasibility studies of a no-implant interatrial shunt, HFpEF/HFmrEF shunts exhibited stability with favorable safety and early efficacy signals. The results show promise toward this new approach for treating patients with HFpEF/HFmrEF and an appropriate hemodynamic profile. (Evaluation of the Safety and Feasibility of a Percutaneously Created Interatrial Shunt to Alleviate Heart Failure Symptoms in Patients With Chronic Heart Failure and Preserved or Mid-Range Left Ventricular Ejection Fraction [ALLEVIATE-HF-1]; NCT04583527; Evaluation of the Safety and Effectiveness of a Percutaneously Created Interatrial Shunt to Alleviate Heart Failure Symptoms in Patients With Chronic Heart Failure and Preserved or Mid-Range Left Ventricular Ejection Fraction [ALLEVIATE-HF-2]; NCT04838353).

Interatrial Shunting for Treating Acute and Chronic Left Heart Failure

The creation of an interatrial shunt has emerged as a new therapy to decompress the left atrium in patients with acute and chronic left heart failure (HF). Current data support the safety of this therapy, and promising preliminary efficacy results have been reported in patients who are refractory to optimal medical/device therapy. This article aims to provide an updated overview and clinical perspective on interatrial shunting for treating different HF conditions, and highlights the potential challenges and future directions of this therapy.

Effects of an interatrial shunt on rest and exercise hemodynamics: results of a computer simulation in heart failure

BACKGROUND

A treatment based on an interatrial shunt device has been proposed for counteracting elevated pulmonary capillary wedge pressure (PCWP) in patients with heart failure and mildly reduced or preserved ejection fraction (HFpEF). We tested the theoretical hemodynamic effects of this approach with the use of a previously validated cardiovascular simulation.

METHODS AND RESULTS

Rest and exercise hemodynamics data from 2 previous independent studies of patients with HFpEF were simulated. The theoretical effects of a shunt between the right and left atria (diameter up to 12 mm) were determined. The interatrial shunt lowered PCWP by ~3 mm Hg under simulated resting conditions (from 10 to 7 mm Hg) and by ~11 mm Hg under simulated peak exercise conditions (from 28 to 17 mm Hg). Left ventricular cardiac output decreased ~0.5 L/min at rest and ~1.3 L/min at peak exercise, with corresponding increases in right ventricular cardiac output. However, because of the reductions in PCWP, right atrial and pulmonary artery pressures did not increase. A majority of these effects were achieved with a shunt diameter of 8-9 mm. The direction of flow though the shunt was left to right in all of the conditions tested.

CONCLUSIONS

The interatrial shunt reduced left-sided cardiac output with a marked reduction in PCWP. This approach may reduce the propensity for heart failure exacerbations and allow patients to exercise longer, thus attaining higher heart rates and cardiac outputs with the shunt compared with no shunt. These results support clinical investigation of this approach and point out key factors necessary to evaluate its safety and hemodynamic effectiveness.

Right-to-left interatrial shunt with hypoxemia caused by a right atrial thrombus

A right-to-left shunt in the presence of normal pulmonary artery pressure is an unusual cause of hypoxemia in an adult who has a patent foramen ovale. We report a rare case of such a shunt-the result of a right atrial thrombus that formed in a hypercoagulable patient after placement of an indwelling central venous catheter for chemotherapy. In order to ascertain the nature of the right atrial mass and to decrease the risk of systemic embolization, the thrombus was surgically removed with the patient on cardiopulmonary bypass.