Prognostic significance of myocardial fibrosis in hypertrophic cardiomyopathy

Myocardial perfusion abnormality in the area of ventricular septum-free wall junction and cardiovascular events in nonobstructive hypertrophic cardiomyopathy

Myocardial perfusion abnormality in the left ventricle is known to be prognostic in patients with hypertrophic cardiomyopathy (HCM). Magnetic resonance imaging and necropsy studies on HCM hearts revealed myocardial lesions predominating in the area of ventricular septum-free wall junction. We assessed perfusion abnormality in this area and correlated it with the prognosis of HCM patients. We performed exercise Tc-99m tetrofosmin myocardial scintigraphy in 55 patients with nonobstructive HCM. Perfusion abnormalities were semiquantified using a 5-point scoring system in small areas of anterior junctions of basal, mid, and apical short axis views in addition to a conventional 17-segment model. All patients were prospectively followed for sudden death, cardiovascular death and hospitalization for heart failure or stroke associated with atrial fibrillation. Cardiovascular events occurred in 10 patients during an average follow-up period of 5.7 years. Stress and rest scores from anterior junction, and conventional summed stress score were significantly higher in patients with cardiovascular events than without (all P < 0.05). Anterior junction stress score of >2 produced a sensitivity of 50% and a specificity of 98% for cardiovascular events and was an independent predictor (hazard ratio 8.33; 95% confidence interval, 1.61-43.5; P = 0.01), with rest scores producing similar values, which were higher than summed stress score of >8 (5.68; 1.23-26.3; P = 0.03). The absence of myocardial perfusion abnormality in the narrow area of anterior junction differentiated HCM patients with low-risk.

Cardiovascular magnetic resonance in the evaluation of heart failure: a luxury or a need?

Heart failure is a common syndrome with multiple causes. Cardiovascular magnetic resonance (CMR), using the available range of technique, is establishing itself as the gold standard noninvasive test for determining the underlying causes, and adding prognostic value, guiding therapy. Progress is continuing and rapid with promising new techniques such as diffuse fibrosis assessment. This article discusses the diverse roles of CMR in heart failure.

Hypertrophic cardiomyopathy and ultra-endurance running - two incompatible entities?

Regular and prolonged exercise is associated with increased left ventricular wall thickness that can overlap with hypertrophic cardiomyopathy (HCM). Differentiating physiological from pathological hypertrophy has important implications, since HCM is the commonest cause of exercise-related sudden cardiac death in young individuals. Most deaths have been reported in intermittent 'start-stop' sports such as football (soccer) and basketball. The theory is that individuals with HCM are unable to augment stroke volume sufficiently to meet the demands of endurance sports and are accordingly 'selected-out' of participation in such events. We report the case of an ultra-endurance athlete with 25 years of > 50 km competitive running experience, with genetically confirmed HCM; thereby demonstrating that these can be two compatible entities.

The role of cardiac MR in new-onset heart failure

In patients with heart failure, cardiovascular magnetic resonance imaging (CMR) allows a multifaceted approach to cardiac evaluation by enabling an assessment of morphology, function, perfusion, viability, tissue characterization, and blood flow during a single comprehensive examination. Given its accuracy and reproducibility, many believe CMR is the reference standard for the noninvasive assessment of ventricular volumes, mass, and function, and offers an ideal means for the serial assessment of disease progression or treatment response in individual patients. Delayed-enhancement (DE)-CMR provides a direct assessment of myopathic processes. This permits a fundamentally different approach than that traditionally taken to ascertaining the etiology of cardiomyopathy, which is vital in patients with nonischemic cardiomyopathy and incidental coronary artery disease and patients with mixed, ischemic and nonischemic cardiomyopathy. Precise tissue characterization with DE-CMR also improves the diagnosis of left ventricular thrombus, for which it is the emerging clinical reference standard. There is a growing body of literature on the utility of CMR for patient risk stratification, and its potential role in important management decisions such as for cardiac resynchronization therapy and defibrillator placement.

Cardiovascular magnetic resonance in heart failure

Imaging has a central role in the evaluation of patients with heart failure (HF). Cardiovascular magnetic resonance (CMR) is rapidly evolving as a versatile imaging modality that often provides additional information to echocardiography in patients with suspected or known HF. CMR is the only imaging modality that has the ability to assess, without exposure to ionizing radiation, cardiac function, structure (tissue characterization), perfusion, and viability. Moreover, magnetic resonance spectroscopy techniques can assess the pathophysiologic role of deranged cardiac energetics in HF. In this review we discuss the role of CMR in the evaluation of patients with HF giving particular emphasis to recent developments and the additional information that can be obtained with this imaging modality, over and above standard echocardiography.

Right ventricular dysfunction is a predictor of non-response and clinical outcome following cardiac resynchronization therapy

BACKGROUND

Cardiac resynchronization therapy (CRT) is an established treatment in advanced heart failure (HF). However, an important subset does not derive a significant benefit. Despite an established predictive role in HF, the significance of right ventricular (RV) dysfunction in predicting clinical benefit from CRT remains unclear. We investigated the role of RV function, assessed by cardiovascular magnetic resonance (CMR), in predicting response to and major adverse clinical events in HF patients undergoing CRT.

METHODS

Sixty consecutive patients were evaluated with CMR prior to CRT implantation in a tertiary cardiac centre. The primary end-point was a composite of death from any cause or unplanned hospitalization for a major cardiovascular event. The secondary end-point was response to therapy, defined as improvement in left ventricular ejection fraction ≥ 5% on echocardiography at one year.

RESULTS

Eighteen patients (30%) met the primary end-point over a median follow-up period of 26 months, and 27 out of 56 patients (48%) were considered responders to CRT. On time-to-event analysis, only atrial fibrillation (HR 2.6, 95% CI 1.02-6.84, p = 0.047) and RV dysfunction, either by a reduced right ventricular ejection fraction-RVEF (HR 0.96, 95% CI 0.94-0.99, p = 0.006) or tricuspid annular plane systolic excursion-TAPSE (HR 0.88, 95% CI, 0.80-0.96, p = 0.006), were significant predictors of adverse events. On logistic regression analysis, preserved RVEF (OR 1.05, 95% CI 1.01-1.09, p = 0.01) and myocardial scar burden (OR 0.90, 95% CI 0.83-0.96, p = 0.004) were the sole independent predictors of response to CRT. Patients with marked RV dysfunction (RVEF < 30%) had a particularly low response rate (18.2%) to CRT.

CONCLUSIONS

Right ventricular function is an important predictor of both response to CRT and long-term clinical outcome. Routine assessment of the right ventricle should be considered in the evaluation of patients for CRT.

Midwall fibrosis is an independent predictor of mortality in patients with aortic stenosis

OBJECTIVES

The goal of this study was to assess the prognostic significance of midwall and infarct patterns of late gadolinium enhancement (LGE) in aortic stenosis.

BACKGROUND

Myocardial fibrosis occurs in aortic stenosis as part of the hypertrophic response. It can be detected by LGE, which is associated with an adverse prognosis in a range of other cardiac conditions.

METHODS

Between January 2003 and October 2008, consecutive patients with moderate or severe aortic stenosis undergoing cardiovascular magnetic resonance with administration of gadolinium contrast were enrolled into a registry. Patients were categorized into absent, midwall, or infarct patterns of LGE by blinded independent observers. Patient follow-up was completed using patient questionnaires, source record data, and the National Strategic Tracing Service.

RESULTS

A total of 143 patients (age 68 ± 14 years; 97 male) were followed up for 2.0 ± 1.4 years. Seventy-two underwent aortic valve replacement, and 27 died (24 cardiac, 3 sudden cardiac deaths). Compared with those with no LGE (n = 49), univariate analysis revealed that patients with midwall fibrosis (n = 54) had an 8-fold increase in all-cause mortality despite similar aortic stenosis severity and coronary artery disease burden. Patients with an infarct pattern (n = 40) had a 6-fold increase. Midwall fibrosis (hazard ratio: 5.35; 95% confidence interval: 1.16 to 24.56; p = 0.03) and ejection fraction (hazard ratio: 0.96; 95% confidence interval: 0.94 to 0.99; p = 0.01) were independent predictors of all-cause mortality by multivariate analysis.

CONCLUSIONS

Midwall fibrosis was an independent predictor of mortality in patients with moderate and severe aortic stenosis. It has incremental prognostic value to ejection fraction and may provide a useful method of risk stratification.

Mechanisms of disease: hypertrophic cardiomyopathy

Hypertrophic cardiomyopathy (HCM) is the most-common monogenically inherited form of heart disease, characterized by thickening of the left ventricular wall, contractile dysfunction, and potentially fatal arrhythmias. HCM is also the most-common cause of sudden cardiac death in individuals younger than 35 years of age. Much progress has been made in the elucidation of the genetic basis of HCM, resulting in the identification of more than 900 individual mutations in over 20 genes. Interestingly, most of these genes encode sarcomeric proteins, such as myosin-7 (also known as cardiac muscle β-myosin heavy chain; MYH7), cardiac myosin-binding protein C (MYBPC3), and cardiac muscle troponin T (TNNT2). However, the molecular events that ultimately lead to the clinical phenotype of HCM are still unclear. We discuss several potential pathways, which include altered calcium cycling and sarcomeric calcium sensitivity, increased fibrosis, disturbed biomechanical stress sensing, and impaired cardiac energy homeostasis. An improved understanding of the pathological mechanisms involved will result in greater specificity and success of therapies for patients with HCM.

Oxidative stress and lectin-like ox-LDL-receptor LOX-1 in atherogenesis and tumorigenesis

Lectin-like oxidized low-density lipoprotein receptor-1 (LOX-1) has been identified as a major receptor for oxidized low-density lipoprotein (ox-LDL) in endothelial cells, monocytes, platelets, cardiomyocytes, and vascular smooth muscle cells. Its expression is minimal under physiological conditions but can be induced under pathological conditions. The upregulation of LOX-1 by ox-LDL appears to be important for physiologic processes, such as endothelial cell proliferation, apoptosis, and endothelium remodeling. Pathophysiologic effects of ox-LDL in atherogenesis have also been firmly established, including endothelial cell dysfunction, smooth muscle cell growth and migration, monocyte transformation into macrophages, and finally platelet aggregation-seen in atherogenesis. Recent studies show a positive correlation between increased serum ox-LDL levels and an increased risk of colon, breast, and ovarian cancer. As in atherosclerosis, ox-LDL and its receptor LOX-1 activate the inflammatory pathway through nuclear factor-kappa B, leading to cell transformation. LOX-1 is important for maintaining the transformed state in developmentally diverse cancer cell lines and for tumor growth, suggesting a molecular connection between atherogenesis and tumorigenesis.

The role of cardiovascular magnetic resonance in pediatric congenital heart disease

Cardiovascular magnetic resonance (CMR) has expanded its role in the diagnosis and management of congenital heart disease (CHD) and acquired heart disease in pediatric patients. Ongoing technological advancements in both data acquisition and data presentation have enabled CMR to be integrated into clinical practice with increasing understanding of the advantages and limitations of the technique by pediatric cardiologists and congenital heart surgeons. Importantly, the combination of exquisite 3D anatomy with physiological data enables CMR to provide a unique perspective for the management of many patients with CHD. Imaging small children with CHD is challenging, and in this article we will review the technical adjustments, imaging protocols and application of CMR in the pediatric population.

Disease pathways and novel therapeutic targets in hypertrophic cardiomyopathy

As described in earlier reviews in this series on the molecular basis of hypertrophic cardiomyopathy (HCM), HCM is one of the archetypal monogenic cardiovascular disorders to be understood at the molecular level. Twenty years after the discovery of the first HCM disease gene, genetic studies still confirm that HCM is principally a disease of the sarcomere. At the biophysical level, myofilament mutations generally enhance Ca(2+) sensitivity, maximal force production, and ATPase activity. These defects ultimately appear to converge on energy deficiency and altered Ca(2+) handling as major common paths leading to the anatomic (hypertrophy, myofiber disarray, and fibrosis) and functional features (pathological signaling and diastolic dysfunction) characteristic of HCM. In this review, we provide an account of the consequences of HCM mutations and describe how specifically targeting these molecular features has already yielded early promise for novel therapies for HCM. Although substantial efforts are still required to understand the molecular link between HCM mutations and their clinical consequences, HCM endures as an exemplar of how novel insights derived from molecular characterization of Mendelian disorders can inform the understanding of biological processes and translate into rational therapies.

CMR in Heart Failure

Heart Failure (HF) is a common syndrome with multiple causes. Cardiovascular magnetic resonance (CMR) is a medical imaging technique with significant advantages, allowing the understanding of aetiology and pathophysiology of HF in the individual patient, permitting specific therapy to be administered and predicting prognosis. This paper discusses the diverse role of CMR in HF.

"Speckled" ventricular septum in hypertrophic cardiomyopathy revisited after 30 years

We found a highly inconsistent relation between the granular and reflective ultrasound ("speckling") pattern frequently observed in the ventricular septum of patients with hypertrophic cardiomyopathy and evidence of myocardial fibrosis by contrast-enhanced cardiovascular magnetic resonance imaging. Therefore, this distinctive echocardiographic appearance of the myocardium does not accurately characterize left ventricular scarring and is most likely explained as an extraneous ultrasound signal pattern. In conclusion, myocardial fibrosis in patients with hypertrophic cardiomyopathy is most reliably identified using contrast-enhanced cardiovascular magnetic resonance imaging.

The fittest person in the morgue?

The cardiovascular benefits of regular physical activity are well established (J. Sci. Med. Sport,7, 2004, 6). James Fixx wrote the best-selling book on running entitled The Complete Book of Running (1977), which led to an increase in popularity. However, when Fixx collapsed and died suddenly while running in 1984, people began to consider the adverse effects of sport on cardiac conditions. Going back in time, in 490 bc Phidippides, a young Greek messenger, ran 26.2 miles from Marathon to Athens delivering the news of the Greek victory over the Persians, and immediately collapsed and died. This is probably the first recorded incident of sudden death of an athlete running a marathon. According to Noakes (Med. Sci. Sports Exerc.,19, 1987, 187), one of the earliest reports on the association between running and cardiac risk was published in 1909, which claimed that school cross-country races over one mile for boys below the age of 19 years were totally inappropriate, and that the associated stress will cause damage in the heart and other organs. Death in athletes is highly publicized and has a substantial emotional impact on the community at large, given that athletes are perceived as the healthiest segment of society.

Late gadolinium enhancement on cardiac magnetic resonance and phenotypic expression in hypertrophic cardiomyopathy

BACKGROUND

Cardiac magnetic resonance (CMR) imaging with late gadolinium enhancement (LGE) can identify areas of myocardial fibrosis in vivo in patients with hypertrophic cardiomyopathy (HCM). The aim of this study was to examine the association between clinical-morphological variables, risk factor for sudden death, and LGE findings in a consecutive, unselected population of HCM patients.

METHODS

From January 2005 to August 2009, 124 HCM patients (53 ± 17 years, 86 men) were prospectively evaluated with CMR examination, assessing left ventricular (LV) hypertrophy, function, and LGE.

RESULTS

In univariate analysis, patients were divided into tertiles according to the number of segments positive for LGE (first tertile, 0.3 ± 0.4; second tertile, 2.2 ± 0.4; third tertile, 5.2 ± 1.9 segments). Male gender (P = .05), maximum LV wall thickness (P = .002), nonsustained ventricular tachycardia (P = .001), ejection fraction <50% (P = .02), LV mass (P = .02), left atrium dilation (P = .04), perfusion defects (P ≤ .001), and telesystolic volume (P = .04) were all positively related with the number of segments of LGE. In multivariable analysis, male gender (P = .007), maximum LV wall thickness (P = .006), LV mass (P = .031), and perfusion alterations (P = .017) were independent predictors of LGE extent.

CONCLUSIONS

Our study shows an independent association, even at multivariate analysis, between the entity of LGE and maximum LV wall thickness, mass, and perfusion defects in patients with HCM. Whether the presence and the extent of LGE translates into clinical events later on awaits further long-term follow-up studies.

New Paradigms in Hypertrophic Cardiomyopathy: Insights from Genetics

Understanding the genetic basis of hypertrophic cardiomyopathy (HCM) provides a remarkable opportunity to predict and prevent disease. HCM is caused by mutations in sarcomere genes and is the most common monogenic cardiovascular disorder. Although unexplained left ventricular hypertrophy (LVH) is considered diagnostic, LVH is not always present. LV wall thickness is often normal until adolescence or later, even in individuals known to carry pathogenic sarcomere mutations. In contrast, genetic testing can identify both individuals who carry pathogenic sarcomere mutations and have a clinical diagnosis of HCM, as well as mutation carriers who have not yet manifest LVH but are at very likely to develop disease. Studying this important new patient subset, designated early or preclinical HCM, allows characterization of the initial consequences of sarcomere mutations, prior to the onset of overt hypertrophic remodeling. Such study has defined novel early phenotypes, including impaired left ventricular relaxation, myocardial energetic deficiencies, and altered collagen metabolism, in mutation carriers with apparently normal cardiac morphology. These results indicate that sarcomere mutations have substantial impact on myocardial function and biochemistry before the onset of frank hypertrophy. Furthermore, animal models of preclinical HCM have identified promising new treatment strategies that may diminish the emergence of overt disease. We can now begin to reshape the paradigm for treating genetic disorders. With improved mechanistic insight and the capability for early diagnosis, genetic advances can lead to new approaches for disease modification and prevention.

Myocardial blood flow and fibrosis in hypertrophic cardiomyopathy

BACKGROUND

We investigated the relationship between myocardial blood flow (MBF), fibrosis, risk factors for sudden death, and clinical manifestations in hypertrophic cardiomyopathy (HCM).

METHODS AND RESULTS

Sixty-two patients with HCM (45 men, overall mean age 47 ± 16 years), 15 acromegalic patients with left ventricular hypertrophy (9 man, overall mean age 47 ± 12 years), and 20 healthy subjects underwent cardiac magnetic resonance. Resting MBF was measured as the ratio between coronary sinus flow measured by phase-contrast technique and left ventricular mass. Myocardial fibrosis was evaluated by late gadolinium enhancement (LGE) technique. In HCM patients, MBF was significantly lower than in control subjects and acromegalic patients. Patients with LGE had lower MBF than those without it (0.46 ± 0.2 vs 0.66 ± 0.29 mL·min(-1)·g(-1); P < .005). Patients with ventricular tachycardia at Holter monitoring had lower MBF (0.4 ± 0.14 vs 0.6 ± 0.29 mL·min(-1)·g(-1); P < .04). Among patients with preserved systolic function, those in New York Heart Association (NYHA) functional class ≥II had lower MBF than those in NYHA functional class I (0.46 ± 0.2 vs 0.69 ± 0.3 mL·min(-1)·g(-1); P < .003). MBF was the only independent predictor of worse clinical status (NYHA ≥II; P = .01).

CONCLUSIONS

In HCM patients low resting MBF is associated with the presence of fibrosis. MBF is a predictor of worse clinical status.

Assessment of myocardial fibrosis with cardiovascular magnetic resonance

Diffuse interstitial or replacement myocardial fibrosis is a common feature of a broad variety of cardiomyopathies. Myocardial fibrosis leads to impaired cardiac diastolic and systolic function and is related to adverse cardiovascular events. Cardiovascular magnetic resonance (CMR) may uniquely characterize the extent of replacement fibrosis and may have prognostic value in various cardiomyopathies. Myocardial longitudinal relaxation time mapping is an emerging technique that could improve CMR's diagnostic accuracy, especially for interstitial diffuse myocardial fibrosis. As such, CMR could be integrated in the monitoring and therapeutic management of a large number of patients. This review summarizes the advantages and limitations of CMR for the assessment of myocardial fibrosis.

Low prevalence of fibrosis in thalassemia major assessed by late gadolinium enhancement cardiovascular magnetic resonance

BACKGROUND

Heart failure remains a major cause of mortality in thalassaemia major. The possible role of cardiac fibrosis in thalassemia major in the genesis of heart failure is not clear. It is also unclear whether cardiac fibrosis might arise as a result of heart failure.

METHODS

We studied 45 patients with thalassaemia major who had a wide range of current cardiac iron loading and included patients with prior and current heart failure. Myocardial iron was measured using T2* cardiovascular magnetic resonance (CMR), and following this, late gadolinium enhancement (LGE) was used to determine the presence of macroscopic myocardial fibrosis.

RESULTS

The median myocardial T2* in all patients was 22.6 ms (range 5.3-58.8 ms). Fibrosis was detected in only one patient, whose myocardial T2* was 20.1 ms and left ventricular ejection fraction 57%. No fibrosis was identified in 5 patients with a history of heart failure with full recovery, in 3 patients with current left ventricular dysfunction undergoing treatment, or in 18 patients with myocardial iron loading with cardiacT2* < 20 ms at the time of scan.

CONCLUSION

This study shows that macroscopic myocardial fibrosis is uncommon in thalassemia major across a broad spectrum of myocardial iron loading. Importantly, there was no macroscopic fibrosis in patients with current or prior heart failure, or in patients with myocardial iron loading without heart failure. Therefore if myocardial fibrosis indeed contributes to myocardial dysfunction in thalassemia, our data combined with the knowledge that the myocardial dysfunction of iron overload can be reversed, indicates that any such fibrosis would need to be both microscopic and reversible.

Risk stratification for sudden cardiac death after septal myectomy

Background

The importance of risk stratification for sudden cardiac death (SCD) after septal myectomy for hypertrophic obstructive cardiomyopathy (HOCM) has not been emphasized previously.

Methods and results

We report 2 patients with SCD or ventricular tachycardia (VT) after septal myectomy for HOCM in whom risk factors for SCD were identified following surgical myectomy. One received an implantable cardioverter-defibrillator (ICD), which subsequently provided appropriate discharges for VT. The other delayed ICD implantation and suffered SCD.

Conclusion

These cases emphasize the importance of risk stratification for SCD after septal myectomy for HOCM.

Myocardial fibrosis in isolated left ventricular non-compaction and its relation to disease severity

AIMS

The aim of the present study was to evaluate the prevalence and extent of myocardial fibrosis in patients with isolated left ventricular non-compaction (LVNC) and to determine its relation to clinical status and LV systolic function.

METHODS AND RESULTS

The cardiac magnetic resonance imaging (MRI) database of our institution was searched for all patients with a first diagnosis of isolated LVNC. The diagnosis of isolated LVNC was based on the presence of standard cardiac MRI and clinical criteria. For each patient, cine and contrast-enhanced cardiac MR images were analysed to evaluate LV systolic function and the prevalence and extent of late gadolinium enhancement (LGE), a surrogate of myocardial fibrosis. A total of 42 patients (mean age 46 ± 20 years, 62% male) were identified. Late gadolinium enhancement was observed in 23 (55%) patients with isolated LVNC, occupying 4.8 ± 6.7% of the LV mass. Both the presence and extent of LGE were significantly related to the number of abnormal clinical features (i.e. symptomatic status, resting electrocardiogram abnormalities, and 24 h Holter monitoring abnormalities; P < 0.001 and P= 0.001, respectively). Similarly, LGE was more prevalent and extensive in patients with LV ejection fraction (EF) < 50% compared with patients with LVEF ≥ 50% (90 vs. 23%; P< 0.001 and 8.9 ± 7.6 vs. 1.1 ± 2.4%; P< 0.001, respectively). At multivariate analysis, both the presence and extent of LV LGE were independently related to LVEF (β = -0.63; P < 0.001 and β = -0.62; P< 0.001, respectively).

CONCLUSION

Myocardial fibrosis is related to clinical disease severity and LV systolic dysfunction in isolated LVNC.

Hypertrophic Cardiomyopathy

Hypertrophic cardiomyopathy is a myocardial disease characterized by myocardial hypertrophy, disorganization of cardiac myocytes, and fibrosis. Twenty-five percent of patients have a dynamic left ventricular outflow tract gradient caused by the combined effects of rapid ventricular ejection, a narrowed outflow tract, and systolic anterior motion of the mitral valve. Most cases are caused by mutations in genes that encode cardiac sarcomeric proteins. Patients present at all ages with chest pain, dyspnea, palpitations, and syncope. The most important complications of the disease are sudden cardiac death, heart failure, and thromboembolism. The principal aims of management are the alleviation of symptoms and the prevention of sudden death. In patients with substantial left ventricular outflow tract obstruction, interventions that reduce the magnitude of the outflow tract gradient (disopyramide, verapamil, β-blockade, alcohol ablation of the interventricular septum, dual-chamber pacing, and surgery) often improve symptoms. Therapeutic options in patients without left ventricular outflow tract obstruction are more limited. Clinical risk stratification is used to estimate the risk of sudden death and to target effective prophylactic treatment with an implantable cardioverter defibrillator.

Device therapy in hypertrophic cardiomyopathy

With increasing awareness of the condition and particular attention being paid to family screening, the number of patients being diagnosed with hypertrophic cardiomyopathy is increasing. Although the majority of patients remain at low risk for sudden cardiac death, all patients need to undergo rigorous and ongoing risk factor stratification in order to best identify those at high risk. Although implantable cardioverter-defibrillators have proven to be effective in the prevention of sudden cardiac death, careful consideration of device implantation in high-risk patients is necessary in view of the potential for device complications and their impact on quality of life.

Cardiac magnetic resonance imaging as a prognostic tool in patients with nonischemic cardiomyopathy

Technical advancements have enabled cardiac magnetic resonance (CMR) imaging to provide a noninvasive assessment of cardiomyopathy. Cardiac magnetic resonance imaging acts as the reference standard for quantifying left and right ventricular function. It also assesses the etiology of cardiomyopathy by demonstrating the presence and size of myocardial scar and by detecting myocardial inflammation and interstitial infiltration. Cardiomyopathy can result in early mortality and arrhythmic risk, and CMR imaging aids in risk stratification among this group of patients. Left ventricular ejection fraction predicts which patients will benefit most from implantable cardioverter-defibrillators (ICDs), but this is not a perfect marker of arrhythmic risk. The etiology of cardiomyopathy, as assessed with CMR imaging, adds further prognostic information with infiltrative cardiomyopathies, resulting in higher mortality than idiopathic cardiomyopathies. Among patients with nonischemic cardiomyopathy (NICM), the degree of fibrosis as determined by the CMR imaging sequence of late gadolinium enhancement (LGE) imaging offers further prognostic information. Late gadolinium enhancement imaging in patients with NICM portends an approximately 3- to 8-fold greater risk of death or hospitalization than NICM without LGE imaging. Further research is needed to determine if the presence of LGE will be helpful in predicting which patients may benefit from ICD implantation.