Right ventricular myocardial infarction in patients with chronic lung disease: possible role of right ventricular hypertrophy

Haemodynamic effects of inhaled nitric oxide in acute myocardial infarction complicated by right heart failure under ECPELLA support: case report

Background

Recently, mechanical support obtained with the combination of venoarterial extracorporeal membrane oxygenation (VA-ECMO) and an Impella device, together referred to as ECPELLA, has been shown to be effective for acute myocardial infarction with cardiogenic shock. However, methods for withdrawing VA-ECMO in acute myocardial infarction cases complicated by right ventricular dysfunction are yet to be established. Here, we report the effective use of inhaled nitric oxide during the weaning of VA-ECMO from the ECPELLA management of a patient with acute myocardial infarction with cardiogenic shock.

Case summary

An 81-year-old man with an acute extensive anterior wall myocardial infarction with cardiogenic shock was supported with ECPELLA to improve his haemodynamics. During ECPELLA, the Impella device could not maintain sufficient flow. Echocardiography revealed a small left ventricle and an enlarged right ventricle, indicating acute right heart failure. Inhaled nitric oxide was initiated to reduce right ventricle afterload, which decreased pulmonary artery pressure from 34/20 to 27/13 mmHg, improved right and left ventricle sizes, and stabilized the Impella support. Afterward, VA-ECMO could be withdrawn because the Impella alone was sufficient for haemodynamic support.

Discussion

Inhaled nitric oxide improved right ventricle performance in a patient with severe myocardial infarction with right heart failure supported by ECPELLA. Thus, we suggest that inhaled nitric oxide facilitates the weaning of VA-ECMO from patients with refractory right ventricular dysfunction who are supported by ECPELLA.

COPD and acute myocardial infarction

COPD is strongly associated with cardiovascular disease, in particular acute myocardial infarction (AMI). Besides shared risk factors, COPD-related factors, such as systemic inflammation and hypoxia, underlie the pathophysiological interaction between COPD and AMI. The prevalence of COPD amongst AMI populations ranges from 7% to 30%, which is possibly even an underestimation due to underdiagnoses of COPD in general. Following the acute event, patients with COPD have an increased risk of mortality, heart failure and arrhythmias during follow-up. Adequate risk stratification can be performed using various imaging techniques, evaluating cardiac size and function after AMI. Conventional imaging techniques such as echocardiography and cardiac magnetic resonance imaging have already indicated impaired cardiac function in patients with COPD without known cardiovascular disease. Advanced imaging techniques such as speckle-tracking echocardiography and T1 mapping could provide more insight into cardiac structure and function after AMI and have proven to be of prognostic value. Future research is required to better understand the impact of AMI on patients with COPD in order to provide effective secondary prevention. The present article summarises the current knowledge on the pathophysiologic factors involved in the interaction between COPD and AMI, the prevalence and outcomes of AMI in patients with COPD and the role of imaging in the acute phase and risk stratification after AMI in patients with COPD.

Right ventricular infarction--diagnosis and treatment

Right ventricular infarction (RVI) as assessed by various diagnostic methods accompanies inferior-posterior wall myocardial infarction (MI) in 30 to 50% of patients. Recognition of the syndrome of RVI is important as it defines a significant clinical entity, which is associated with considerable immediate morbidity and mortality and has a well-delineated set of priorities for its management. Patients may clinically present with hypotension, elevated jugular venous pulse (JVP), and occasionally shock, all in the presence of clear lung fields. The ST-segment elevation of > or = 0.1 mV in the right precordial leads V4R is a readily available electrocardiographic sign used for diagnosis of RVI. Other diagnostic approaches for assessing RVI include echocardiography, radionuclide ventriculography, technetium pyrophosphate scanning, and hemodynamic measurements. The proper management of RVI includes volume loading to maintain adequate right ventricular preload, ionotropic support, and maintenance of atrioventricular synchrony. Reperfusion therapy should be initiated at the earliest signs of right ventricular dysfunction. Finally, complete recovery over a period of weeks to months is a rule in a majority of patients, suggesting right ventricular "stunning" rather than irreversible necrosis has occurred.

Pathophysiology of acute myocardial infarction

More than 80% of acute myocardial infarcts are the result of coronary atherosclerosis with superimposed luminal thrombus. Uncommon causes of myocardial infarction include coronary spasm, coronary embolism, and thrombosis in nonatherosclerotic normal vessels. Additionally, concentric subendocardial necrosis may result from global ischemia and reperfusion in cases of prolonged cardiac arrest with resuscitation. Myocardial ischemia shares features with other types of myocyte necrosis, such as that caused by inflammation, but specific changes result from myocyte hypoxia that vary based on length of occlusion of the vessel, duration between occlusion and reperfusion, and presence of collateral circulation.

Is left coronary system more susceptible to atherosclerosis than right?

On the basis of pathological, angiographical, intravascular ultrasound and computed tomography data coronary atherosclerosis appears to be more prevalent in the left coronary arterial system compared to the right. However, the pathophysiological mechanisms implicated in this discrepancy largely remain uncertain. The hemodynamic or anatomical differences between the right and left coronary artery might play a key role. Physiologically, the right coronary flow is more uniform during the cardiac cycle compared to the left, which experiences a remarkable systolic decline accompanied by a significant diastolic increment. Thus, the oscillatory shear stress, that constitutes a proved atherogenic factor, is more intense in regions with disturbed flow in the left coronary system. Likewise, the wall stress is more oscillatory during the cardiac cycle in the left coronary artery. On top of that, several differences regarding the anatomical configuration (3D geometry, branching) and the phasic motion between the right and the left arterial system appear to play a critical role in the modulation of the local atherogenic environment. Therefore, it could be assumed that the flow characteristics along with the geometrical and phasic motion patterns generate an intense oscillation of the imposed to the arterial wall stresses, especially in the left coronary artery. Over the long-term, these augmented oscillatory stresses, in combination with the effect of systemic risk factors, might modulate a more atherogenic environment in the atherosclerosis-prone regions of the left coronary system.

Electrocardiographic Diagnosis of ST-elevation Myocardial Infarction

The ECG is an essential part of the initial evaluation of patients who have chest pain, especially in the immediate decision-making process in patients who have ST-elevation myocardial infarction. This article reviews and summarizes the current information that can be obtained from the admission ECG in patients who have ST-elevation acute myocardial infarction, with an emphasis on: (1) prediction of final infarct size, (2) estimation of prognosis, and (3) the correlations between various ECG patterns and the localization of the infarct and the underlying coronary anatomy.

Acute coronary syndromes

Despite technologic advances in many diagnostic fields, the 12-lead ECG remains the basis for early identification and management of an acute coronary syndrome. This article reviews the use of the ECG in acute coronary syndromes.

The electrocardiogram in ST elevation acute myocardial infarction: correlation with coronary anatomy and prognosis

The electrocardiogram is considered an essential part of the diagnosis and initial evaluation of patients with chest pain. This review summarises the information that can be obtained from the admission electrocardiogram in patients with ST elevation acute myocardial infarction, with emphasis on: (1) prediction of infarct size, (2) estimation of prognosis, and (3) the correlations between various electrocardiographic patterns and the localisation of the infarct and the underlying coronary anatomy.

Unusual electrocardiographic presentation of an isolated right ventricular myocardial infarction secondary to thrombotic occlusion of a non-dominant right coronary artery--a case report and brief review of literature

Isolated right ventricular infarction is an extremely rare phenomenon. Its electrocardiographic (ECG) features may be misinterpreted or even missed if not suspected. A case of an isolated right ventricular myocardial infarction is presented, recognized by ST-segment elevation in a single precordial lead, such as V1, aided thereafter by right precordial ECG changes. Immediate coronary angiography revealed proximal occlusion of a small non-dominant right coronary artery. Coronary intervention as well as infusion of intravenous normal saline solution and pressor agent for hypotension provided symptomatic relief, and subsequent recovery from this potentially life-threatening, but rare condition. Routine 12-lead ECG done approximately 12 hours after the admission showed extension of ST segment elevation from V1 trough V3 without any ST-segment elevation in inferior leads. This case demonstrates that there might be a very unusual ECG appearance in the setting of an isolated right ventricular myocardial infarction and can be missed if not immediately suspected. Isolated right ventricular myocardial infarction may be difficult to recognize, requiring both a high index of clinical suspicion for its presence, as well as careful evaluation of unusual ECG features of the disease entity.

Electrocardiographic diagnosis of acute myocardial infarction: Current concepts for the clinician

BACKGROUND

Over the past 2 decades, the 12-lead electrocardiogram has attained special significance for the diagnosis and triage of patients with chest pain because timely detection of myocardial injury and a rapid assessment of myocardium at risk proved pivotal to implementing effective reperfusion therapies during acute myocardial infarction. However, this wealth of information could still be underutilized by clinicians who may restrict their diagnostic quest in patients with chest pain to the more classic electrocardiographic signs.

METHODS

The medical literature on electrocardiographic manifestations of acute myocardial infarction was extensively reviewed.

RESULTS

The widespread utilization of both coronary angiography and methods to determine myocardial function and metabolism in patients with acute myocardial infarction over the last 10 years has provided the means for rigorous comparisons with electrocardiographic information. We summarize these electrocardiographic signs and patterns in terms of their relevance to the clinician to help reduce the incidence of "nondiagnostic electrocardiograms" and improve timely decision-making.

CONCLUSIONS

The electrocardiogram continues to be an invaluable tool in the initial evaluation of patients with chest pain. The plethora of data currently available on electrocardiographic changes correlating with myocardial injury allows clinicians to make faster and better decisions than ever before.

Right ventricular involvement in acute myocardial infarction

The presence of right ventricular dysfunction in patients with acute myocardial infarction has important implications. It is a marker for in-hospital mortality and failure to recognize it may lead to inappropriate treatment with serious consequences for the patient. Patients surviving the acute event do, however, have a relatively good long-term prognosis.

Right ventricular regional wall motion abnormality in congenital heart disease

Four cases of congenital heart disease with right ventricular overload and echocardiographic evidence of persistent right ventricular regional wall motion abnormalities are presented. Right ventricular infarction could be a possibility. Such regional wall motion abnormalities could add to overall right ventricular dysfunction in these cases. Echocardiography is useful in diagnosis. Right ventricular wall motion abnormalities should be studied in detail in all cases of congenital heart disease with right ventricular overload.

Isolated right ventricular infarction

Our experience with 18 cases of isolated right ventricular infarction is reported and the literature is reviewed. Chronic lung disease with right ventricular hypertrophy is an important risk factor. Chest pain is the usual symptom at presentation but some cases can have breathlessness, palpitations or syncope. Some cases can have sinus bradycardia, atrial fibrillation or ventricular tachycardia. Atrioventricular block is rare. Cases with pulmonary artery hypertension, extensive right ventricular infarction due to proximal occlusion of the right coronary artery, right atrial infarction or atrial fibrillation can have hypotension and/or systemic venous congestion. A surface electrocardiogram mainly showing changes in leads conventionally considered to represent left ventricle and right-sided chest leads may not show an infarct pattern in some cases. Echocardiography is, therefore, more reliable in diagnosing this condition. The cautious use of small doses of nitrates and diuretics is not hazardous in the absence of hypotension. High doses of steroids and anti-coagulants can be helpful. The prognosis is usually good, although sudden collapse can occur due to ventricular fibrillation, rupture of the right ventricular free wall or a massive pulmonary embolism.

Frequency of chronic obstructive airways disease and pulmonary hypertension in patients with acute inferior myocardial infarction with or without right ventricular infarction

OBJECTIVE

Factors influencing the incidence of right ventricular infarction among patients with acute inferior myocardial infarction have not yet been fully established. Chronic obstructive airways disease and right ventricular hypertrophy were suggested as possible predisposing factors but no definite evidence was shown. This study analyses the frequency of chronic obstructive airway disease and of Doppler assessed pulmonary hypertension among patients with acute inferior myocardial infarction with or without right ventricular infarction.

DESIGN AND PATIENTS

Sixty consecutive patients with acute inferior myocardial infarction were prospectively enrolled into the study.

MEASUREMENTS

Standard 12-lead ECG with right precordial leads (V3-6R) were recorded on admission to the Coronary Care Unit and on days 2 and 3. Doppler echocardiography was performed within 48 h after the onset of myocardial infarction and repeated 6 weeks later together with a pulmonary function test. Routine biochemical and clinical data were collected.

RESULTS

Right ventricular infarction occurred in 35% of patients with acute inferior myocardial infarction. No differences in respiratory indices of chronic obstructive airways disease or in Doppler echocardiography parameters of pulmonary hypertension were revealed among patients with and without right ventricular infarction. Peak total creatine kinase level and creatine kinase myocardial isoenzyme levels were higher in patients with right ventricular infarction than in those without (2925 +/- 1321 vs. 1682 +/- 1216 U/l; P < 0.001 and 207 +/- 108 vs. 127 +/- 102 U/l; P < 0.05, respectively).

CONCLUSIONS

In the course of acute inferior myocardial infarction, the frequencies of chronic obstructive airways disease and/or pulmonary hypertension were not higher among patients with right ventricular infarction than among those without right ventricular infarction. Thus, history of chronic obstructive airways disease and/or pulmonary hypertension do not necessitate specific precautions in respect of right ventricular infarction.

Ischemia right ventricular dysfunction

For many years ischemic heart disease involving the right ventricle had received little attention. During the last 15 years, the initial works of Cohn, Isner, and others spawned a number of clinical and experimental studies that extended the understanding of the pathophysiology of ischemia in the right ventricle. Most of the work has been done in the setting of acute myocardial infarction, and information is still lacking in other conditions, such as chronic ischemic heart disease and perioperative right ventricular dysfunction. Acute right ventricular infarction rarely occurs in the absence of left ventricular necrosis and in most cases is the extension of an inferior left ventricular infarct. The majority of patients with right ventricular infarction only exhibit subtle signs of ischemic dysfunction. Elevated right atrial pressure is found only in the typical syndrome of elevated venous pressure; low output syndrome can be found only in 20% of the cases, and cardiogenic shock secondary to right ventricular necrosis is found only in 10%. It is also important to note that there is not a clear correlation between the severity of ischemic right ventricular dysfunction and the necrotic area. The discrepancy may be due to ischemia without necrosis of the right ventricular wall (stunned myocardium), but the intact pericardium and the necrosis of the interventricular septum may also play an important role. In the most severe form of ischemic right ventricular dysfunction, the entire right ventricular wall is akinetic. Right atrial, right ventricular, and pulmonary artery pressures become similar in magnitude and shape, and the pulmonary valve is opened during diastole, demonstrating a passive blood flow from the right atrium to the left ventricle through the low resistance pulmonary capillary bed. Volume loading, administration of dopamine or dobutamine, and careful use of vasodilators under hemodynamic monitoring are the therapeutic measures to control the severe forms of acute ischemic right ventricular dysfunction. The use of thrombolytic agents has decreased the incidence of right ventricular dysfunction after acute myocardial infarction. Mortality is high in the severe forms of acute ischemic right ventricular dysfunction, but after discharge from hospital the prognosis is good and right heart failure is unusual, even in those patients with shock during the first days of evolution of the infarct.

Isolated right ventricular infarction

The literature on isolated right ventricular infarction is reviewed and local experience is reported. Chronic lung disease is an important risk factor. Chest pain and breathlessness are common. Syncope and sudden collapse can also occur. Rhythm disorders include sinus bradycardia, atrial fibrillation and ventricular tachycardia or fibrillation. Atrioventricular block is rare. Hypotension and a right-sided fourth heart sound are common. Cautious use of slow-release nitroglycerin is not hazardous in the absence of hypotension. High doses of steroids and anticoagulants can be helpful. The prognosis is usually good, although sudden collapse can occur due to ventricular fibrillation, rupture of the right ventricular free wall or massive pulmonary embolism.

Right ventricular infarction

Right ventricular infarction commonly occurs in association with acute inferior left ventricular infarction, but is uncommon when infarction involves other areas of the left ventricle. Evidence of right ventricular infarction often can be detected by physical examination, electrocardiography, echocardiography, or radionuclide ventriculography. However, hemodynamically significant infarction (i.e., hypotension or shock) is much less frequent, occurring in approximately 10% of patients with other evidence of right ventricular infarction. Right ventricular infarction increases ventricular stiffness, thereby impeding diastolic filling. This results in hemodynamic changes similar to those found in constrictive pericarditis: elevated systemic venous pressure, a Y descent greater than the X descent, and an inspiratory increase in venous pressure. The increase in venous pressure generally equals or even exceeds left atrial pressure. When hypotension or shock occurs, expansion of vascular volume is generally employed as initial therapy. In nonresponders, dobutamine or similar inotropic agents may be helpful. The prognosis during the acute phases is guarded, but, in survivors, prognosis is favorable and generally related to the extent of left ventricular involvement.

Electrocardiographic manifestations of right ventricular infarction

RVI is a frequent occurrence in the setting of an acute inferoposterior myocardial infarction and its early recognition has important therapeutic and prognostic implications. Because of this, diverse invasive and noninvasive diagnostic techniques have been investigated to identify patients with RVI. Electrocardiography is the most available, simple, and objective of these techniques. Numerous ECG signs of RVI have been described and some of them, especially ST segment elevation and patterns of necrosis (QS, QR) in the right precordial leads (V3R to V5R), have a very high sensitivity, specificity, and positive predictive value for the detection of RVI. ST segment elevation in lead V4R is also helpful in identifying the occluded coronary artery in patients with acute myocardial infarction, which could have great importance in their management. Hence, a 12-lead ECG with the right precordial leads (V3R to V6R) should be a routine part of the initial evaluation of patients with clinical suspicion of acute inferior myocardial infarction. This article reviews the value, limitations, and pathogenesis of the ECG manifestations of RVI.

Right ventricular hypertrophy is an important determinant of right ventricular infarction complicating acute inferior left ventricular infarction

To explore the role of right ventricular hypertrophy and chronic obstructive pulmonary disease in the pathogenesis of right ventricular infarction, 27 consecutive patients with a first inferior left ventricular infarction were prospectively studied. Right ventricular infarction was diagnosed using established hemodynamic criteria. Right ventricular hypertrophy was defined as right ventricular free wall thickness greater than or equal to 5 mm. Patients were classified into two groups: Group I patients with right ventricular infarction (n = 15), and Group II patients without right ventricular infarction (n = 12). The ratio of forced expiratory volume over forced vital capacity (FEV1/FVC) and forced expiratory flow between 25 and 75% expired volume (FEF) as a percent of predicted values were significantly reduced in Group I versus Group II (90 +/- 5 versus 105 +/- 6% and 63 +/- 13 versus 103 +/- 15%, respectively; p less than 0.05). This was associated with increased right ventricular wall thickness (Group I 5.5 +/- 0.3 mm versus Group II 3.9 +/- 0.2 mm, p less than 0.001). Multiple logistic regression analysis demonstrated that right ventricular wall thickness was the strongest predictor of right ventricular infarction (p less than 0.0005). No significant difference was found in the site of right coronary occlusion, collateral blood supply or extent of coronary artery disease between the two groups. These findings suggest that right ventricular hypertrophy predisposes patients with acute inferior myocardial infarction to right ventricular infarction independent of the site or extent of coronary artery disease.