Right ventricular myocardial infarction
I. What every physician needs to know.
When approaching patients with acute right heart failure or acute-on-chronic right heart failure, it is important to consider the diagnosis of right ventricular infarction. This diagnosis should also be considered in patients presenting with a myocardial infarction, especially inferior myocardial infarctions.
Classically, patients with a right ventricular infarction present with hypotension and signs of elevated right heart pressure, namely elevated jugular venous pulsations. However, the presentation can be variable depending on factors such as the degree of accompanying left ventricular dysfunction and the patient’s volume status. To establish the diagnosis, clinicians will need to request right-sided precordial electrocardiographic leads and cardiac biomarkers, as well as consider requesting an echocardiogram.
Early on, clinicians must consider the hemodynamic implications of a right ventricular infarction. A healthy right ventricle pumps the same cardiac output as the left ventricle but it pumps against the low resistance of the pulmonary vasculature. Therefore it has less muscle mass and is suited for much less cardiac work. In the setting of a right ventricular infarction, the right ventricle can have both diastolic and systolic dysfunction resulting in impaired filling and reduced contractility.
This results in a reliance on increased volume/preload to maintain stroke volume in the setting of a reduced ejection fraction. Therefore, an impaired right ventricle may require an expansion of circulating plasma volume to maintain preload, while therapies that reduce preload, such as nitroglycerin, may have deleterious effects on systemic blood pressure.
II. Diagnostic Confirmation: Are you sure your patient has right ventricular infarction?
The diagnosis of right ventricular infarction is made by the physical examination, use of cardiac biomarkers to identify myocardial infarction, electrocardiographic findings, and cardiac imaging.
A. History Part I: Pattern Recognition:
The original description of a right ventricular infarction included the triad of hypotension, clear lung fields and elevated jugular venous pulsations. However, depending on the presence of coexisting left ventricular infarction, patients can also present with signs of left heart failure. Another typical presentation would include a patient with symptoms of myocardial ischemia that develops marked hypotension after administration of nitrogylcerin or morphine.
B. History Part 2: Prevalence:
Depending on the definition and study methods utilized, the reported incidence is variable. Right ventricular infarctions are most commonly seen in inferior myocardial infarctions and can complicate up to 50% of inferior myocardial infarctions. Right ventricular infarctions are seen in only about 10% of anterior myocardial infarctions. Isolated right ventricular infarctions are rare and account for less than 3% of all myocardial infarctions.
These numbers can be explained by considering the typical blood supply to the right ventricle. The right coronary artery supplies blood flow to the bulk of the right ventricle, including the lateral wall, and in most patients also continues on to supply blood flow to the posterior and inferior aspects of the left ventricle. A proximal right coronary artery occlusion would therefore impair blood flow to both the right ventricle and the inferior left ventricle. An isolated right ventricular infarction would require disease of specific branches of the right coronary artery or a non-dominant right coronary artery.
The left coronary artery and its branches supply much less blood flow to the right ventricle. A dominant left circumflex artery can supply blood flow to the right ventricle but an occlusion of such a vessel would also impair blood flow to the inferior left ventricle. Branches of the left anterior descending artery can also supply blood flow to aspects of the right ventricular anterior wall. Thus, occlusion of the the left anterior descending artery and anterior left ventricular infarctions can be complicated by associated right ventricular involvement.
C. History Part 3: Competing diagnoses that can mimic right ventricular infarction.
Other diagnoses to consider in patients with acute right heart failure include acute pulmonary embolism, pulmonary hypertension, pericardial disease such as tamponade or constrictive pericarditis, primary valve disorders such endocarditis of the tricuspid valve, and right heart failure from left heart disease.
D. Physical Examination Findings.
Findings on physical exam are an important clue to the diagnosis of right ventricular infarction. Remembering that the classic description of a patient with a right ventricular infarction includes hypotension and clear lung fields. Elevated neck veins can also be helpful and these aspects of the physical exam should be evaluated. It is especially important to perform a dedicated examination of the neck veins. The most sensitive physical exam finding for right ventricular infarction is the presence of elevated jugular venous pressure.
In an acute presentation, it would be unusual to see other findings of severe right heart failure such as peripheral edema, ascites or hepatic enlargement. Another sensitive exam finding is the Kussmaul sign, which is increased filling of the neck veins during inspiration. This exam finding, commonly associated with constrictive pericarditis, is a consequence of impaired filling of a stiff, ischemic right ventricle. Other notable exam findings described in the setting of right ventricular infarction include right-sided gallops on cardiac auscultation, pulsusparadoxus, and the murmur of tricuspid regurgitation if there is papillary muscle dysfunction or marked dilatation of the right ventricle.
E. What diagnostic tests should be performed?
The most informative diagnostic tests to evaluate for a right ventricular infarction are an electrocardiogram (with both the standard 12 leads and right-sided precordial leads), cardiac biomarkers and a transthoracic echocardiogram. Other imaging studies, such as cardiac magnetic resonance imaging, may provide clues to the diagnosis but are not necessary in routine care. One other diagnostic test deserves special mention; invasive hemodynamic measurements with a pulmonary artery catheter. The typical hemodynamic patterns of right ventricular infarctions are well-described but beyond the scope of this chapter. It is important to note though that these measurements are rarely necessary to make the initial diagnosis of a right ventricular infarction but may be helpful in guiding therapy in select patients.
Given the importance of the electrocardiogram to the diagnosis of right ventricular infarction, this diagnostic test deserves special comment. Current ACC/AHA guidelines for patients with ST-elevation myocardial infarction (STEMI) recommend right-sided electrocardiographic leads in all patients with an inferior STEMI (class I recommendation, level of evidence B). Obtaining right precordial electrocardiographic leads means placing 4 additional leads on the right chest in a similar fashion to V3-V6 in the standard 12-lead electrocardiogram. V2 becomes V1R, V1, which becomes V2R, and the lead opposite of V3 becomes V3R, and so on.
The most sensitive electrocardiographic finding in a right ventricular infarction is ST segment elevation in lead V4R. However, it is important to remember that electrocardiographic changes can be transient and not all patients with a right ventricular infarction will have ST segment elevations on right-sided precordial leads. If clinical suspicion for a right ventricular infarction is high and right-sided precordial leads do not reveal ST segment elevations, a transthoracic echocardiogram should be obtained.
1. What laboratory studies (if any) should be ordered to help establish the diagnosis? How should the results be interpreted?
As is discussed in the chapter on acute myocardial infarction, cardiac biomarkers are utilized to identify and quantify infarction.
2. What imaging studies (if any) should be ordered to help establish the diagnosis? How should the results be interpreted?
An echocardiogram can help differentiate between a right ventricular infarction and other causes of hypotension with signs of elevated right heart filling pressures, namely pericardial tamponade.
F. Over-utilized or “wasted” diagnostic tests associated with this diagnosis.
III. Default Management.
Management of a right ventricular infarction includes the usual care for acute coronary syndrome including antiplatelet agents, anticoagulation, statin therapy, and consideration for revascularization. However, management of a right ventricular infarction also includes anticipating complications, namely hypotension, bradycardic arrhythmias, and other atrial arrhythmias.
A. Immediate management.
Hypotension is a common problem in patients with a right ventricular infarction and should be anticipated. Medications that may reduce preload should be avoided or given with a high degree of caution; such medications include diuretics, nitrates, opioids, angiotensin-converting enzyme (ACE) inhibitors, and beta-blockers. When hypotension is present, a trial of 250-500cc of intravenous fluid should be administered and the patient should be monitored for a change in blood pressure.
Even though patients with a right ventricular infarction are dependent on preload, administering extra circulating volume may not always be beneficial. For instance, a dilated right ventricle can cause bowing of the interventricular septum into the left ventricle and/or increased intrapericardial pressure, both of which can impair left ventricular cardiac output. Also, if there is associated left ventricular dysfunction, then administering fluid may lead to pulmonary edema.
If right ventricular preload is optimized and the patient still has hypotension then more advanced interventions will be required. This includes the following: treatment for arrhythmias as outlined below, treatment of concomitant left ventricular dysfunction, inotropic support with agents such as dobutamine, and mechanical support with devices such as intra-aortic balloon pumps or ventricular assist devices.
Another set of complications that should be anticipated are arrhythmias, especially atrioventricular blocks and atrial fibrillation. In addition to supplying blood flow to the right ventricle, the right coronary artery supplies blood flow to the AV node in most patients and AV node ischemia and high degree atrioventricular block is common in patients with a right ventricular infarction. Patients should be monitored for bradycardia and may need temporary pacing to maintain adequate heart rates.
In addition, the impaired right ventricle can be dependent on atrial function to maintain preload. Sinus node dysfunction, complete atrioventricular block, and atrial arrhythmias such as atrial fibrillation can all disrupt atrioventricular synchrony and have profound effects on hemodynamics. Dual chamber pacing or restoration of sinus rhythm may be necessary to maintain cardiac output.
V. Transitions of Care
A. Sign-out considerations While Hospitalized.
Contingency plans for patients with a right ventricular infarction should discuss how to address hypotension and arrhythmias and a reminder on what medications to avoid.
F. Prognosis and Patient Counseling.
Even without revascularization, the right ventricle can often recover a good amount of systolic function in the months following an infarction. In the absence of severe left ventricular dysfunction, most patients with a right ventricular infarction have a favorable long-term prognosis though some studies have suggested right ventricular infarction is an independent risk factor for increased long-term mortality. It is quite clear though that in patients with an inferior myocardial infarction, involvement of the right ventricle portends a worse short-term prognosis with increased in-hospital mortality from the associated complications discussed above.
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- I. What every physician needs to know.
- II. Diagnostic Confirmation: Are you sure your patient has right ventricular infarction?
- A. History Part I: Pattern Recognition:
- B. History Part 2: Prevalence:
- C. History Part 3: Competing diagnoses that can mimic right ventricular infarction.
- D. Physical Examination Findings.
- E. What diagnostic tests should be performed?
- 1. What laboratory studies (if any) should be ordered to help establish the diagnosis? How should the results be interpreted?
- 2. What imaging studies (if any) should be ordered to help establish the diagnosis? How should the results be interpreted?
- F. Over-utilized or “wasted” diagnostic tests associated with this diagnosis.
- III. Default Management.
- A. Immediate management.
- V. Transitions of Care
- A. Sign-out considerations While Hospitalized.
- F. Prognosis and Patient Counseling.