Right-to-left shunting through a patent foramen ovale in right ventricular infarction: improvement of hypoxemia and hemodynamics with inhaled nitric oxide

New application of saline contrast-enhanced electrical impedance tomography method for right ventriculography besides lung perfusion: detection of right-to-left intracardiac shunt

AIM

Saline contrast-enhanced electrical impedance tomography (EIT) has been used to identify the respiratory failure etiologies through assessment of regional lung perfusion at the bedside. In this study, we introduce a novel approach to detect right-to-left intracardiac shunt based on the center of heart (CoH) parameter determined from the early phase of impedance-time curve after saline bolus injection.

METHODS AND RESULT

The timepoints when the saline bolus enter the heart (T0) and the lung regions (T1) are identified at first. A moving time window from T0 to T1 is then generated with steps of 0.5 s and the slope of the impedance-time curve in each pixel within the window calculated. CoH is calculated as the geometric center of pixel slope values in the right-to-left image direction. To illustrate how this method works in practice, we calculated the CoH values at T0 to T1 in 10 control hypoxic patients with no right-to-left shunt. In addition, we examined two critically ill patients with right-to-left intracardiac shunt. One was postcardiac surgery patient who had a residual atrial septal defect by color doppler of transesophageal echocardiograph. The other patient had a congenital heart disease of ventricular septal defect by color doppler of trans-thoracic echocardiography. A large difference in CoH between T0 to T1 was observed in the two patients with intracardiac shunt than in the control patients (11.06 ± 3.17% vs. 1.99 ± 1.43%, P = 0.030).

CONCLUSION

Saline bolus EIT for lung perfusion might be used as ventriculography to identify the right-to-left intracardiac shunt at the bedside.

Optimal Conservative Management Resolves Refractory Hypoxemia in Patient with Right Myocardial Infarction Complicated by PFO-Induced Shunting

Inferior myocardial infarction is often accompanied by infarction of the right ventricle (RV). Uncommon RV infarction cases with patent foramen ovale (PFO) shunt, leading to severe persistent hypoxemia even without any pulmonary embolism involvement and often requiring invasive intervention, have been documented previously. We report a patient with RV infarction and right-to-left shunt via PFO who improved with only early revascularization and optimal standard treatment. This condition may not necessitate any invasive intervention if it is treated and monitored per standard procedures. Clinicians should consider the possibility of a right-to-left shunt in patients with RV infarction and persistent hypoxemia to implement appropriate therapeutic interventions.

Percutaneous Closure of the Patent Foramen Ovale on Right Ventricular Mechanical Circulatory Support

Right ventricular infarction can precipitate severe right-to-left shunting and refractory hypoxia from a previously dormant patent foramen ovale. Right ventricle mechanical circulatory support and patent foramen ovale closure can play a crucial role in the treatment of hypoxia and right ventricular recovery. We report a case of successful percutaneous patent foramen ovale closure on right ventricle mechanical circulatory support in a patient with right ventricular shock. (Level of Difficulty: Intermediate.)

The dilemma of refractory hypoxemia after inferior wall myocardial infarction

Patent foramen ovale (PFO) occurs in 25% of people. The decision on whether to close the PFO found after myocardial infarction and specifically right ventricular infarction is debated, with no solid guidelines addressing this subject. Here we present the case of a 59-year-old man who presented with a myocardial infarction and was found to have PFO. He was treated with revascularization of the culprit artery, followed by supportive care.

Refractory hypoxaemia following inferior ST-segment elevation myocardial infarction: case report of an unusual complication and review of treatment strategies

Right ventricular (RV) infarction is not an uncommon complication of acute left ventricular infarction. It has been established that RV dysfunction post myocardial infarction (MI) is associated with increased mortality and morbidity. When RV infarction occurs in a patient with previously dormant patent foramen ovale (PFO), an unusual presentation of persistent refractory hypoxaemia ensues. We present a case of new RV infarction in a patient with underlying ischaemic cardiomyopathy, which was complicated by acute right-to-left shunting through the PFO. He was treated with percutaneous coronary intervention (PCI) and subsequent percutaneous PFO closure. We will also review the existing literature with regards to diagnostic and management strategies for patients with this unusual sequelae of MI.

Nitric oxide therapy for post-laparoscopic surgery associated patent foramen ovale: incidence, mechanisms, diagnosis and therapy

OBJECTIVE

Postoperative hypoxemia is a common clinical challenge. The diagnosis of an underlying cause of hypoxemia may not immediately be apparent. Clinically silent and non-functional intracardiac shunt may become apparent and pose significant management problems in the postoperative period.

DATA SOURCE

We describe a case where clinically significant hypoxemia resulted from a patent foramen ovale (PFO) after laparoscopic surgery due to changes in the intra-abdominal and intrathoracic pressures.

CONCLUSION

This condition was effectively diagnosed by bedside echocardiography, and was effectively treated with nitric oxide.

Acute right to left shunt through patent foramen ovale presenting as hypoxemia after myocardial infarction: a case report

Introduction

This is a report of a 56-year-old man who became hypoxic due to an acute right to left shunt after sustaining a myocardial infarction involving the right ventricle. This case provides the opportunity to review several key pathophysiologic concepts in the setting of acute right ventricular infarction. Although the development of an acute right to left shunt is a rare complication of myocardial infarction, it is important to recognize the diagnosis early in order to prevent life threatening or debilitating clinical sequelae that may result from tissue hypoxia and embolic events. Transesophageal echocardiography is the noninvasive study of choice to confirm the diagnosis. Treatment involves optimization of right ventricular function to minimize shunting. However, medical therapy may provide only temporary relief, and closure of the atrial septal defect should be considered if a clinically significant shunt persists.

Case presentation

A 56-year-old Caucasian man with severe aortic insufficiency presented to the emergency department for evaluation of substernal chest pain. An inferior myocardial infarction was diagnosed by the electrocardiogram and serologic markers. Cardiac catheterization revealed complete occlusion of the right coronary artery as well as a 50-75% stenosis of the left anterior descending artery. Angioplasty of the right coronary artery was performed, but immediate re-occlusion occurred. Subsequently, hypotension and severe hypoxemia developed and persisted despite intubation and mechanical ventilation with 100% oxygen. A significant right-to-left shunt through a patent foramen ovale was diagnosed by contrast transesophageal echocardiogram. Surgical intervention was required and included coronary artery bypass grafting, aortic valve replacement as well as closure of his atrial septal defect.

Conclusion

A right to left atrial shunt is a rare complication of inferior myocardial infarction with right ventricular infarction. The diagnosis should be considered in the presence of inferior myocardial infarction when hypoxemia persists despite administration of 100% oxygen. Early diagnosis and treatment are critical in order to reduce the risk of embolization and to prevent end-organ damage due to hypoxemia.

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.

Transcatheter Device Closure of Interatrial Septal Defects in Patients with Hypoxia

BACKGROUND

There has been growing interest in transcatheter closure of interatrial septal defects (IASDs) for a variety of indications, but reports are limited in patients with hypoxia from right-to-left shunting.

METHODS

Between August 2000 and October 2004, 181 patients were referred to our institution for elective closure of a patent foramen ovale (PFO) or atrial septal defect (ASD). Among these patients, 10 (5.5%) underwent closure for hypoxia due to persistent or intermittent right-to-left shunting. Clinical evaluation, including echocardiography with color Doppler and agitated saline, was performed in all patients to determine the degree of right-to-left shunting. Defects were closed with Amplatzer (n = 4) or Cardioseal (n = 6) devices, under transesophageal (TEE) or intracardiac echocardiography (ICE) guidance.

RESULTS

Mean age was 62.7 years (range: 31-88 years) with 70% female. Characteristics for closure included four patients with persistent hypoxia and six with intermittent hypoxia, including two with platypnea-orthodeoxia syndrome. All patients had echocardiography showing moderate (n = 6) or severe (n = 4) shunting. Patients had significant comorbidities, including chronic lung disease requiring supplemental oxygen (n = 5) and congestive heart failure (n = 2). TEE guidance was used in three patients, and ICE was performed in the remainder. Mean closure device diameter was 27 mm. Mean preprocedural arterial oxygen saturation of 86.7% improved to 95.9% immediately after closure, with color Doppler and agitated saline revealing the absence of (n = 5) or mild (n = 5) shunting. In-hospital major complications were limited to one patient with a transient ischemic attack after an initially unsuccessful closure attempt.

CONCLUSIONS

Percutaneous closure of IASDs in a heterogeneous group of patients with hypoxia can be safely and effectively performed. The procedure results in immediate arterial saturation improvement and reduced right-to-left shunting.

Right ventricular infarction complicated by right to left shunting through an atrial septal defect: successful treatment with an Amplatzer septal occluder

A 68 year old woman presented with right ventricular myocardial infarction complicated by refractory hypoxaemia. She was found to have a significant right to left shunt at the atrial level through a previously undiagnosed ostium secundum atrial septal defect. Percutaneous closure of the atrial septal defect with an Amplatzer septal occluder resulted in prompt improvement in her oxygenation and clinical state. Such closure should be considered for patients with right ventricular infarction and refractory hypoxaemia caused by a right to left interatrial shunt.

Hemodynamic effects of inhaled nitric oxide in right ventricular myocardial infarction and cardiogenic shock

OBJECTIVES

We sought to determine whether or not inhaled nitric oxide (NO) could improve hemodynamic function in patients with right ventricular myocardial infarction (RVMI) and cardiogenic shock (CS).

BACKGROUND

Inhaled NO is a selective pulmonary vasodilator that can decrease right ventricular afterload.

METHODS

Thirteen patients (7 males and 6 females, age 65 +/- 3 years) presenting with electrocardiographic, echocardiographic, and hemodynamic evidence of acute inferior myocardial infarction associated with RVMI and CS were studied. After administration of supplemental oxygen (inspired oxygen fraction [F(i)O(2)] = 1.0), hemodynamic measurements were recorded before, during inhalation of NO (80 ppm at F(i)O(2) = 0.90) for 10 min, and 10 min after NO inhalation was discontinued (F(i)O(2) = 1.0).

RESULTS

Breathing NO decreased the mean right atrial pressure by 12 +/- 3%, mean pulmonary arterial pressure by 13 +/- 2%, and pulmonary vascular resistance by 36 +/- 8% (all p < 0.05). Nitric oxide inhalation increased the cardiac index by 24 +/- 11% and the stroke volume index by 23 +/- 12% (p < 0.05). The NO administration did not change systemic arterial or pulmonary capillary wedge pressures. Contrast echocardiography identified three patients with a patent foramen ovale and right-to-left shunt flow while breathing at F(i)O(2) = 1.0. Breathing NO decreased shunt flow by 56 +/- 5% (p < 0.05) and was associated with markedly improved systemic oxygen saturation.

CONCLUSIONS

Nitric oxide inhalation results in acute hemodynamic improvement when administered to patients with RVMI and CS.