Approach Considerations
Right ventricular infarction should always be considered in any patient who has inferior wall myocardial infarction and associated hypotension, especially in the absence of rales. In patients with right ventricular dysfunction and shock, the focus is on ensuring adequate right-sided filling pressures. If cardiogenic shock persists after optimization of right ventricular end-diastolic pressure, inotropic therapy should be considered.
Concomitant left ventricular dysfunction may necessitate use of an intra-aortic balloon pump and/or nitroprusside infusion for afterload reduction.
Because of the critical role of atrioventricular synchrony in maintaining cardiac output, atrioventricular sequential pacing is the modality of choice when a pacemaker is required. [37]
A study by Lupi-Herrera et al indicated that primary percutaneous coronary intervention (PPCI) leads to lower mortality rates than does thrombolytic therapy in patients with right ventricular infarction. Patients were divided into three groups: those without right ventricular failure, those with right ventricular failure, and those with cardiogenic shock. Of all of them, 148 patients underwent thrombolytic therapy and 351 patients were treated with PPCI. In-hospital mortality rates at 30 days were as follows [38] :
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Patients without right ventricular failure: Thrombolytic therapy (4.4%); PPCI (3.2%)
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Patients with right ventricular failure: Thrombolytic therapy (13%); PPCI (8.3%)
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Patients with cardiogenic shock: Thrombolytic therapy (100%); PPCI (44%)
Right Ventricular Dysfunction and Shock
Right ventricular failure may limit left heart filling via a decrease in CO, ventricular interdependence, or both. Treatment of patients with right ventricular dysfunction and shock has traditionally focused on ensuring adequate right-sided filling pressures to maintain CO and adequate left ventricular preload; however, patients with cardiogenic shock due to right ventricular dysfunction have very high right ventricular end-diastolic pressure, often greater than 20 mm Hg.
This elevation of right ventricular end-diastolic pressure may result in shifting of the interventricular septum toward the left ventricular cavity, which raises left atrial pressure but impairs left ventricular filling due to the mechanical effect of the septum bowing into the left ventricle. The alteration in geometry also impairs left ventricular systolic function. [17] Careful administration of fluid boluses, used in conjunction with noninvasive or invasive assessment of cardiac output, is recommended (500-1000 mL). [27]
Inotropic Therapy in Cardiogenic Shock
Inotropic therapy should be considered for right ventricular failure when cardiogenic shock persists after right ventricular end-diastolic pressure has been optimized. [27, 39] Right ventricular end-diastolic pressure of 10-15 mm Hg has been associated with maximal cadiac output, but marked variability exists in optimal values.
Inotropes that can be used in right ventricular failure are dobutamine, milrinone, levosimendan (approved only in Europe), norepinephrine, and, possibly, low-dose vasopressin. Avoid dopamine and phenylephrine. [27]
Management of Persistent Hypotension
If hypotension persists, consider hemodynamic monitoring with a pulmonary artery catheter, keeping in mind the following admonitions concerning right ventricular perforation: patients with extensive right ventricular necrosis are at risk for right ventricular catheter–related perforation, and passage of a floating balloon catheter or pacemaker must always be performed with care.
Early Treatment Survival Benefit
Current available evidence indicates that patients presenting within 6 hours of onset of inferior wall myocardial infarction with right ventricular involvement diagnosed by electrocardiography (ECG) or other noninvasive criteria have a survival benefit from pharmacologic or mechanical reperfusion therapy. [9, 10, 33, 34, 40, 41]
Scant data exist regarding improvement in patients who present later than 12 hours after onset, and these patients most likely would do well with a conservative management strategy, considering the often spontaneous resolution of right ventricular dysfunction. [42]
Inhaled Nitric Oxide
The use of inhaled nitric oxide has been of interest to treat patients with right ventricular infarctions complicated by cardiogenic shock. The principle behind this treatment is that by specifically decreasing pulmonary vascular resistance without compromising systemic vascular resistance, the filling of the left ventricle can be improved with a resultant improvement of systemic cardiac output. Utilization of inhaled nitric oxide in this setting has been associated with rapid improvement of hemodynamics. [43]
Beta-blocking agents and angiotensin-converting enzyme inhibitors improve right ventricular hemodynamics in patients with biventricular failure and have theoretical benefits in isolated right ventricular failure, but their role in the latter is poorly studied. [27]
Valve Replacement and Repair
Severe tricuspid regurgitation in the setting of acute right ventricular infarction can be managed with either valve replacement or repair with angioplasty rings, because the incompetent valve may serve as a mechanical impediment to maintenance of adequate cardiac output. Finally, should a patient develop arterial hypoxemia secondary to right-to-left shunting at the atrial level, then an atrial septal defect–occluding device should be considered. However, if for any reason a delay occurs in placement of the occluding device, inhaled nitric oxide can decrease the right-to-left shunting and increase systemic oxygenation. [43]
Mechanical circulatory support can be also used, including a left ventricular assist device (LVAD), right ventricular assist device (RVAD), or biventricular ventricular assist device. [27]
Kretzchmar et al developed a novel percutaneously implantable RVAD, the PERKAT system, which appears to have the potential to offer emergency support of up to 3 L/min. [44] This system is designed to implant through the femoral vein and consists of a self-expandable chamber covered with multiple inflow valves carrying foils; a flexible outlet tube with a pigtail tip is attached to the distal end. [44]
Tables
Leads |
Sensitivity (%) |
Specificity (%) |
V1 |
28 |
92 |
V3 R |
69 |
97 |
V4 R |
93 |
95 |
