This is usually the initial and preferred diagnostic test in the assessment of heart failure.5) Its use to distinguish systolic heart failure is critical in decision-making about drugs and devices such as implantable devices or ventricular assist device.6) Decreased LV ejection fraction has been associated with poor prognosis.6) In addition to assessment of ventricular size and systolic function, echocardiography can provide information about diastolic, valvular function and hemodynamic status.5) Sequential echocardiography is widely used for monitoring the evolution of the condition and response to therapy. While this latter application is considered appropriate especially in patients with a change in clinical status (appropriateness score 9),7) the large (> 10%) confidence intervals of ejection fraction measured with 2-dimensional echocardiography suggest this may not be a useful tool for identification of subtle changes.8)

Some echocardiographic features can provide clues to the causative etiology of heart failure, although tissue characterization with other imaging such as CMR is often required to clarify the differential diagnosis. For example, specific patterns of regional wall motion abnormalities suggest coronary artery disease. Distinction of this from the regional heterogeneity of dilated cardiomyopathy may be supported by ischemic or viable responses to either exercise or pharmacologic stress echocardiography,9) as well as coronary imaging with CT and scar imaging with CMR. Likewise, ambiguity about the cause of LV thickening in hypertensive heart failure may be elucidated by techniques characterizing myocardial infiltration. Finally, while apical ballooning or mid to basal ballooning can be a clue of stress-induced cardiomyopathy (SCMP),10)11) other testing may be needed to exclude acute myocardial infarction (AMI).

Although echocardiography is extremely versatile and readily accessible, image quality is often limited, and geometric assumptions are required to quantify LV systolic function. Furthermore, it lacks the ability to provide more detailed tissue characterization, which can be extremely important in defining the etiology of heart failure. CMR is currently considered the gold standard for the assessment of LV mass, systolic function, and assessment of myocardial fibrosis. CMR has the ability to image in any three dimensional plane, offering the ability to produce extremely accurate and reproducible assessment of LV and right ventricular (RV) volumes, ejection fraction, and mass, without relying on geometric assumptions that can result in significant miscalculations particularly in dilated ventricles.12)13)

In addition, CMR offers the ability to assess myocardial perfusion as well as implementing other imaging techniques [delayed hyperenhancement (DHE) imaging, T1-weighted, T2-weighted, and fat suppression imaging techniques] to assess for myocardial fibrosis as well as myocardial edema. DHE imaging allows for the identification of myocardial fibrosis with high resolution and offers the ability to differentiate between types of cardiomyopathies, based on patterns of fibrosis (Fig. 1).14)15) DHE-CMR can identify significant coronary artery disease and decrease the need of conventional coronary angiography in patients presenting with heart failure of uncertain etiology.16) T1- or T2-weighted image sequences provide the ability to differentiate between fat, muscle, and areas of inflammation, based on the different proton relaxation properties of these tissues. Tissue edema appears bright on T2-weighted images in both acute coronary syndromes as well as inflammatory processes such as cardiac sarcoidosis or myocarditis.17)18) Myocardial edema may occur in isolation, but is often accompanied by characteristic patterns of myocardial fibrosis, which has the ability to elucidate the etiology of decreased ventricular function. The standard T2-weighted image sequences use turbo spin-echo sequences, and have been limited by artifacts (e.g., posterior wall signal loss caused by through-plane motion or bright rim artifacts caused by stagnant blood along the endocardial surface).19) However, recent advances in T2-weighted methods have been developed which have demonstrated increased diagnostic accuracy and may improve the reliability of CMR edema imaging.18)19)

Although DHE sequences on CMR is widely utilized for assessing regional myocardial fibrosis/scarring this relies on the relative difference in signal intensity between scarred and the presumed normal adjacent myocardium to generate image contrast. Scar formation in infarcted myocardium is due to replacement of the myocardium with collagen. Such areas of dense fibrosis have a much slower washout rate of gadolinium-based contrast than healthy myocardium, thus resulting in markedly increased signal intensity on T1-weighted imaging within the infarcted myocardium. A key shortcoming to delayed contrast-enhanced CMR is that it relies on the assumption that the surrounding and remote myocardium is truly normal and that there is a distinct difference in gadolinium washout kinetics. Because collagen deposition in nonischemic cardiomyopathy is commonly diffuse, the technique of delayed contrast enhancement often shows no regional scarring.

However, T1 mapping allows for the calculation of the relaxation time of each pixel within a parametric image, which can detect subtle differences in regional tissue characteristics. Therefore, contrast resolution not dependent on relative differences in signal intensity as it is with DHE scar imaging. Therefore, this newer CMR technique may prove to be useful in evaluating various reversible cardiomyopathies. Several techniques for measuring myocardial T1 to identify myocardial fibrosis with T1 mapping have been described in the literature.18)20)21)

Myocarditis, immune and viral mediated cardiac damage, is about 15% of the patients with a new onset dilated cardiomyopathy or heart failure.22) Despite up to 50% of patients have no identifiable etiology with a full and complete evaluation, the determination of the etiology is important in the treatment and prediction of the prognosis.22)

Peripartum cardiomyopathy is a rare cardiomyopathy of unknown etiology that occurs in the peripartum period (from 1 month before delivery to 5 months postpartum).26) The diagnosis requires both the absence of an identifiable cause for the heart failure and recognizable heart diseases prior to the last month of pregnancy. Because there are no available population-based studies and symptoms of early heart failure are similar to symptoms experienced by many women in the last month of a normal pregnancy, the incidence of peripartum cardiomyopathy is unknown. Risk factors include multiparity, advanced maternal age, multifetal pregnancy, preeclampsia, gestational hypertension, and African-American race.26) Because the multifetal pregnancy rate has risen rapidly over the last decades, the incidence of peripartum cardiomyopathy may have increased.27)

The possible mechanisms for this cardiomyopathy include myocarditis, abnormal immune responses to pregnancy, abnormal hemodynamic response to increased blood volume in pregnancy, and prolonged use of tocolytics.26)

Symptoms and signs that may suggest heart failure include paroxysmal nocturnal dyspnea, chest pain, cough, jugular venous distension, new onset cardiac murmurs and pulmonary crackles. As there are no specific criteria for differentiating the subtle symptoms of heart failure from symptoms of normal late pregnancy, the diagnosis of peripartum cardiomyopathy is usually based on the echocardiographic demonstration of new onset LV systolic dysfunction. Echo-cardiographic patterns include diffuse hypokinesia with increased LV diastolic dimensions.28) Patients with initial severe LV systolic dysfunction and larger LV dimensions seem unlikely to regain normal LV function on follow-up.28)29)

Myocardial inflammation and fibrosis can be detected by CMR in the acute stages. Several case studies and one case series demonstrated that patients with DHE had worse outcomes than those who did not.30)31) Furthermore, myocardial inflammation seen in the acute phases on T2-weighted images was transient in most cases, and DHE may regress in some patients.31)

In addition to the use of standard therapy for heart failure (diuretics, vasodilators and digoxin), prolactin inhibition32) may provide potential benefit to patients with peripartum cardiomyopathy. Careful attention must be paid to select drugs relatively safe for mother and fetus and to exclude those that can evoke fetal abnormalities. The duration of treatment is still unknown. Though the majority of peripartum cardiomyopathy patients recover partially or are completely improved with treatment, the reported mortality rates lie between 18% and 56%.26)33) Moreover, subsequent pregnancy in these patients can be associated with a recurrence of peripartum cardiomyopathy and can result in death.33)

SCMP is a syndrome of reversible LV systolic dysfunction with characteristic apical ballooning in patients without significant epicardial coronary artery stenosis.10)34) This syndrome, also known as Takotsubo cardiomyopathy, is believed to be associated with various clinical scenarios, especially with intense mental or emotional stress.35) However, physical stress can cause this kind of cardiomyopathy. Park et al.35) reported their data of patients admitted to the medical intensive care unit. They reported 28% of patients showed apical ballooning and they were usually associated with hypotension, sepsis, cardiomegaly and use of inotropic agents.

SCMP occurs usually in women over 50 years of age, and the typical features include profound mental stress immediately preceding and triggering the cardiac events, acute retrosternal chest pain with ST-segment change and/or T-wave inversion, absence of significant coronary artery stenosis by coronary angiography, and LV systolic dysfunction with abnormal wall motion of apex (apical ballooning).11) There is a variant of apical ballooning syndrome. Transient mid- and basal-ventricular ballooning is a new variant of the transient LV apical ballooning syndrome. The involvement of the LV's mid- and basal-ventricle with sparing of the apical segment is the unique finding of this variant.36) Because the guideline excludes the presence of pheochromocytoma in the diagnosis of SCMP, the presence of a specific pattern with pheochromocytoma should be classified as catecholamine-induced cardiomyopathy.37)

Echocardiography is a useful method to diagnose this type of cardiomyopathy. Transthoracic echocardiography usually demonstrates LV systolic dysfunction with typical apical ballooning and/or midventricular hypokinesia, and the wall-motion abnormality extends beyond the distribution of any of one single coronary artery.10)11) Transient LV hypokinesia can be restricted to the midventricular segment and/or basal segment without involvement of the apical segment in a minor population.36) The involvement of RV can be observed in 26% of patients, and seems to be associated with the presence of more severe LV systolic dysfunction and pleural effusion.38)

CMR can be useful in the assessment of SCMP. The distinction between an ischemic process vs. SCMP can be difficult at times. Patients who have the left anterior descending coronary artery thrombus which then recannulated can appear to have no significant disease on coronary angiogram, and may mistakenly be diagnosed with SCMP. Furthermore, patients with microvascular obstruction may have normal appearing epicardial vessels on coronary angiography. CMR can differentiate between ischemic etiologies and SCMP with perfusion imaging, T2-weighted imaging and DHE. Patients with SCMP typically have characteristic wall motion defects similar to that seen in anteroapical infarction. Patients with SCMP may have small areas of subtle DHE in a pattern that is distinctly different from DHE seen in patients with myocardial fibrosis.39)40) Myocardial edema may also be present in these segments on T2-weighted images.40)41) Furthermore, a recent multicenter study using CMR demonstrated that SCMP may also present in other patterns of myocardial dysfunction, such as biventricular dysfunction, mid-ventricular dysfunction, and basal dysfunction. Patients in this study who had no DHE demonstrated complete recovery of the LV function on follow-up CMR.

However, SCMP can be misdiagnosed as AMI, and AMI can be misdiagnosed as SCMP.42) The recent guidelines for the diagnosis of SCMP37) define this entity on the basis of acute LV apical ballooning, after exclusion of AMI. Although there is lack of agreement on the necessity of coronary angiography, either this or coronary CT is usually performed to exclude coronary occlusion. DHE-CMR may be used in the identification of the presence of a significant coronary artery disease and decrease the need of conventional coronary angiography.16)

The treatment of SCMP is similar to that of ischemic LV dysfunction. However, the prognosis of SCMP is good, with rapid recovery within a week.11)37) For this reason, not only is appropriate imaging an important step to confirm the diagnosis, but follow-up imagine is often performed to confirm resolution.

Prolonged tachycardia can cause reversible cardiomyopathy.60) Sustained rapid atrial or ventricular pacing for about 24 hours can cause severe biventricular systolic and diastolic dysfunction in animal models.61) In a human series, various arrhythmias caused tachycardia-induced cardiomyopathy including atrial fibrillation, atrial tachycardia, accessory pathway associated tachycardias, atrioventricular node reentry tachycardia and ventricular tachycardia associated with LV systolic dysfunction. Frequent ventricular premature complexes can be associated with transient LV systolic dysfunction.62)

The precise mechanisms responsible for developing cardiomyopathy are unknown. The proposed mechanisms include myocardial energy depletion and impaired utilization of energy, myocardial ischemia, abnormal regulation of cardiac calcium metabolism, and remodeling of cardiomyocytes and extracellular matrix.60)

Tachycardia-induced cardiomyopathy can occur in any age group. Although the ventricular rate that causes tachycardia-induced cardiomyopathy has not been determined in humans, clinicians should suspect it when LV systolic dysfunction accompanies persistent tachycardia (> 100 beats/minute).63) The main differential diagnosis is increased sympathetic activity and tachycardia due to reduced stroke volume.

Echocardiography usually shows left and right ventricular dilatation and decreased systolic function, but this can occur in association with other forms of heart disease.64) CMR can provide precise assessment of LV and RV function and volumes. Tachycardia-induced cardiomyopathy should not result in DHE. The presence of DHE and the pattern of this finding should raise the suspicion of an alternative etiology for LV dysfunction, based on the pattern of fibrosis.

This type of LV systolic dysfunction can improve rapidly (often within 4 weeks) with intervention or correction of the underlying cause of their tachycardia,65) but complete reverse remodeling may be slow (6 months or more). Recognition of this entity allows institution of heart rate control, although this may be ineffective, especially in atrial fibrillation, perhaps reflecting a role of variation in RR interval as well as tachycardia.66) Therapies include medications lowering heart rate, cardioversion or radiofrequency ablation of arrhythmias, and antiarrhythmic surgery.63) Even though LV function normalizes rapidly with treatment, recurrent tachycardia can cause rapid decline in LV function, development of heart failure and sudden cardiac death.65)

Deficiencies of nutrients, electrolytes or trace elements can cause LV systolic dysfunction. Sometimes these patients exhibit other symptoms of deficiencies, i.e., patients with hypophosphatemia show skeletal muscle weakness.67) These deficiencies are usually associated with malnutrition, intoxication or misuse of illegal drugs. Correction of these deficiencies can improve LV systolic function with time.

Some patients with hypertensive and alcoholic cardiomyopathy recover with treatment. Also, some patients with myocardial infiltrative diseases like hemochromatosis76) and light chain deposition disease77) can be normalized with treatment. Though anthracycline-induced cardiomyopathy is largely irreversible and cumulative, some patients show a reversible course.78)