Intermittent atrial level right-to-left shunt with temporary hypoxemia in a patient during support with a left ventricular assist device

Successful recovery from refractory hypoxia due to right-to-left shunting associated with iatrogenic atrial septal defect after catheter ablation in a patient with a left-ventricular assist device: a case report

Background

Catheter ablation (CA) has been reported to be an effective therapeutic option for ventricular arrhythmias, even in patients with a left-ventricular assist device (LVAD). However, the issues of right-to-left shunting due to iatrogenic atrial septal defect (iASD) associated with procedures for CA have not been well documented. We describe a rare case of refractory hypoxia associated with right-to-left shunting via iASD after CA through the transseptal approach in an LVAD patient.

Case summary

A 52-year-old Asian man with a continuous-flow implantable LVAD and progressive right ventricular (RV) dysfunction was admitted because of refractory ventricular tachycardia (VT) and subsequent right heart failure. Since VT could not be controlled by intravenous administration of multiple antiarrhythmic drugs, VT ablation via the transseptal approach was performed. Ventricular tachycardia was terminated to the sinus rhythm after VT ablation; however, hypoxia associated with significant right-to-left shunting across the iASD was detected. Intensive medical management, such as an adjusted mechanical ventilator to increase pulmonary vascular compliance and adjustment of LVAD pump speed, as well as the use of intravenous inotropes to support impaired RV function successfully stabilized the haemodynamic and improved hypoxia for the disappearance of right-to-left shunting. Echocardiography at 7 months after CA showed that the significant iASD and right-to-left shunting had disappeared.

Discussion

The evaluation of RV function prior to VT ablation via the transseptal approach is important in the postoperative management of patients with LVAD, because RV dysfunction may cause refractory hypoxia due to iASD.

Left ventricular assist device placement in the setting of congenital VSD

We describe the management of a 59-year-old female with an unrepaired congenital ventricular septal defect (VSD) and end stage nonischemic cardiomyopathy necessitating placement of a left ventricular assist device (LVAD) as a destination treatment. Simultaneous repair of the VSD was performed during the LVAD implantation under a beating heart. The patient remained hemodynamically stable throughout her postoperative course, without signs of hypoxia or cyanosis. Following discharge, outpatient surveillance echocardiogram demonstrated successful VSD closure and no residual shunt.

Expanding the Scope of Multimodality Imaging in Durable Mechanical Circulatory Support

An increasing number of patients transition to advanced-stage heart failure refractory to medical therapy. Left ventricular assist systems (LVAS) provide a bridge to candidates awaiting heart transplantation and extended device durability allows permanent implantation referred to as destination therapy. Noninvasive imaging plays a pivotal role in the optimal management of patients implanted with durable mechanical circulatory support (MCS) devices. Several advances require an updated perspective of multi-modality imaging in contemporary LVAS management. First, there has been substantial evolution of devices such as the introduction of the fully magnetically levitated HeartMate 3 pump (Abbott, Abbott Park, Illinois). Second, imaging beyond the device, of the peripheral system, is increasingly recognized as clinically relevant. Third, U.S. Food and Drug Administration recalls have called attention to LVAS complications beyond pump thrombosis that are amenable to imaging-based diagnosis. Fourth, there is increased availability of multimodality imaging, such as computed tomography and positron emission tomography, at many centers across the world. In this review, the authors provide a practical and contemporary approach to multi-modality imaging of current-generation durable MCS devices. As the use of LVAS and other novel MCS devices increases globally, it is critical for clinicians caring for LVAS patients to understand the roles of various imaging modalities in patient evaluation and management.

Right-to-Left Shunt During Transseptal Mitral Valve-in-Valve Replacement: A Case Report

The following case report details an 88-year-old woman with severe mitral stenosis and moderate mitral regurgitation who presented with worsening dyspnea on exertion. The patient had undergone 4-vessel coronary artery bypass graft and mitral valve replacement 14 years before and was deemed high risk for redo sternotomy. A transseptal mitral valve-in-valve replacement was performed which resulted in intraoperative hypoxia and hypotension after atrial septal defect creation for valve deployment. A right-to-left shunt had developed due to the patient's underlying pulmonary hypertension. Successful atrial septal defect closure resolved the hypoxia and hypotension. The patient had a brief and uncomplicated postoperative course.

Diagnostic Bedside Ultrasonography for Acute Respiratory Failure and Severe Hypoxemia in the Medical Intensive Care Unit: Basics and Comprehensive Approaches

Bedside goal-directed ultrasound is a powerful tool for rapid differential diagnosis and monitoring of cardiopulmonary disease in the critically ill patient population. The bedside intensivist is in a unique position to integrate ultrasound findings with the overall clinical situation. Medically critically ill patients who require urgent bedside diagnostic assessment fall into 2 categories: (1) acute respiratory failure and (2) hemodynamic derangements. The first portion of this review outlines the diagnostic role of bedside ultrasound in the medically critically ill patient population for the diagnosis and treatment of acute respiratory failure, acute respiratory distress, and severe hypoxemia. The second portion will focus on the diagnostic role of ultrasound for the evaluation and treatment of shock states, as well as describe protocolized approaches for evaluation of shock during cardiopulmonary resuscitation. Different respiratory system pathologies that result in acute respiratory failure (such as increased interstitial fluid, alveolar consolidation, pleural effusion) cause characteristic ultrasonographic findings; diaphragmatic assessment may also add information. Intracardiac shunting can cause severe hypoxemia. Protocolized approaches for the evaluation of patients with acute respiratory failure or distress are discussed.

Amplatzer™ occlusion device implantation in a patient with biventricular HeartWare®

There have been several reports of right-to-left shunting through patent foramen ovale (PFO) after implantation of a left ventricular assist device (LVAD). The atrial pressure changes after assist implantation leading to revelation of undetected PFOs may cause severe systemic hypoxemia. A percutaneous closure approach has been shown to be an adequate therapy option in patients with LVAD. We report a successful interventional occlusion of a PFO with right-to-left shunt in a patient with biventricular HeartWare® ventricular assist device (HVAD) support.

The ABCs of left ventricular assist device echocardiography: a systematic approach

Echocardiography is an important imaging modality used to determine the indication of left ventricular assist device (LVAD) implantation for patients with advanced heart failure (HF) and for serial follow-up to make management decisions in patient care post-implant. Continuous axial-flow LVAD therapy provides effective haemodynamic support for the failing left ventricle, improving both the clinical functional status and quality of life. Echocardiographers must develop a systematic approach to echocardiographic assessment of LVAD implantation and post-LVAD implant cardiac morphology and physiology. This approach must include the evaluation of left and right heart chamber morphology and physiology and the anatomy and physiology of the inflow and outflow cannulas and the rotor pump, and the determination of the degree of tricuspid regurgitation and the presence of interatrial shunts and aortic regurgitation. Collaboration among the echocardiography and HF/transplant teams is essential to obtain this comprehensive evaluation. We outline a systematic approach to evaluating patients with HF who have failed conventional therapy and require LVAD therapy as a bridge to cardiac transplantation or destination therapy.

Delayed intracardial shunting and hypoxemia after massive pulmonary embolism in a patient with a biventricular assist device

We describe the interdisciplinary management of a 34-year-old woman with dilated cardiomyopathy three months postpartum on a cardiac biventricular assist device (BVAD) as bridge to heart transplantation with delayed onset of intracardial shunting and subsequent hypoxemia due to massive pulmonary embolism. After emergency surgical embolectomy pulmonary function was highly compromised (PaO₂/FiO₂ 54) requiring bifemoral veno-venous extracorporeal membrane oxygenation. Transesophageal echocardiography detected atrial level hypoxemic right-to-left shunting through a patent foramen ovale (PFO). Percutaneous closure of the PFO was achieved with a PFO occluder device. After placing the PFO occluder device oxygenation increased significantly (Δ p_aO₂ 119 Torr). The patient received heart transplantation 20 weeks after BVAD implantation and was discharged from ICU 3 weeks after transplantation.

An increase in pulmonary vascular resistance in patients on BVAD can reopen a PFO resulting in atrial right-to-left shunting and subsequent hypoxemia. The case demonstrates the usefulness of transesophageal echocardiography examinations in the detection of this unexpected event. Percutaneous placement of a PFO occluder device is an appropriate strategy to stop intracardiac shunting through PFO in fixed elevation of pulmonary vascular resistance.

Perioperative echocardiographic examination for ventricular assist device implantation

Ventricular assist devices (VADs) are systems for mechanical circulatory support of the patient with severe heart failure. Perioperative transesophageal echocardiography is a major component of patient management, and important for surgical and anesthetic decision making. In this review we present the rationale and available data for a comprehensive echocardiographic assessment of patients receiving a VAD. In addition to the standard examination, device-specific pre-, intra-, and postoperative considerations are essential to the echocardiographic evaluation. These include: (a) the pre-VAD insertion examination of the heart and large vessels to exclude significant aortic regurgitation, tricuspid regurgitation, mitral stenosis, patent foramen ovale, or other cardiac abnormality that could lead to right-to-left shunt after left VAD placement, intracardiac thrombi, ventricular scars, pulmonic regurgitation, pulmonary hypertension, pulmonary embolism, and atherosclerotic disease in the ascending aorta; and to assess right ventricular function; and (b) the post-VAD insertion examination of the device and reassessment of the heart and large vessels. The examination of the device aims to confirm completeness of device and heart deairing, cannulas alignment and patency, and competency of device valves using two-dimensional, and color, continuous and pulsed wave Doppler modalities. The goal for the heart examination after implantation should be to exclude aortic regurgitation, or an uncovered right-to-left shunt; and to assess right ventricular function, left ventricular unloading, and the effect of device settings on global heart function. The variety of VAD models with different basic and operation principles requires specific echocardiographic assessment targeted to the characteristics of the implanted device.

Hypoxemia Complicating LVAD Insertion: Novel Application of the Amplatzer PFO Occlusion Device

We report a case of profound systemic hypoxemia complicating left ventricular assist device (LVAD) insertion due to right to left shunting through a patent foramen ovale (PFO) in association with a Chiari network. The patient was successfully managed with percutaneous closure of the interatrial defect using an Amplatzer PFO occlusion device and judicious reduction in LVAD flows.

Profound hypoxemia resulting from shunting across an inadvertent atrial septal tear after left ventricular assist device placement

Defects within the interatrial septum (IAS) can be a source of significant right-to-left shunting and hypoxemia, particularly after placement of a left ventricular assist device (LVAD). We report a case of LVAD placement in which an unrecognized IAS tear occurred intraoperatively, leading to profound arterial desaturation. Transesophageal echocardiography (TEE) was instrumental in making the diagnosis. Certain intraoperative events increased the pressure gradient between the right and left atria, aggravating hypoxemia. We recommend that patients undergoing LVAD placement be screened intraoperatively with TEE for unrecognized IAS defects. Re-examination of the IAS should occur on weaning from cardiopulmonary bypass.

IMPLICATIONS

A traumatic atrial septal defect after atrial cannulation caused a right-to-left intracardiac shunt on initiation of left ventricular assist device support that was further aggravated by chest closure and pleural suction, culminating in severe hypoxemia.

A complication with the use of a centrifugal pump during thoraco-abdominal aortic surgery

IMPLICATIONS

Centrifugal pumps used to enable atrio-femoral bypass may trigger a change in intra-cardiac shunt flow and increase the risk of morbidity and mortality.

Right hemidiaphragmatic elevation with a right-to-left interatrial shunt through a patent foramen ovale: a case report and literature review

A right-to-left shunt (RLS) is an uncommon complication of a patent foramen ovale (PFO) that may cause hypoxemia from venous admixture and ischemic complications from paradoxic embolization. This report presents the third described patient whose RLS through a PFO and profound hypoxemia developed in association with right hemidiaphragm dysfunction (but without a pressure gradient driving the right-to-left flow). In addition to extending the available experience with this unusual clinical event, we report on the successful closure of the PFO by a catheter-deployed double-umbrella device, after the positioning of which the patient's oxygenation normalized.

The evaluation and management of hypoxemia in the chronic critically ill patient

Hypoxemia is a prevalent problem in the chronically critically ill patient. This article reviews the pathophysiologic mechanisms of hypoxemia in this patient population, discusses how oxygenation is evaluated, and reviews methods for delivery of oxygen. Other topics directly related to oxygen use, such as oxygen toxicity, heliox use, and portable oxygen devices, are included.