Repolarization abnormalities detected by magnetocardiography in patients with dilated cardiomyopathy and ventricular arrhythmias

Repolarization Abnormalities by Magnetocardiography. Introduction: Abnormal repolarization is one of the acknowledged mechanisms leading to malignant ventricular arrhythmias. We used a novel magnetocardiographic technique to investigate the role of inhomogeneous repolarization in patients with nonischemic dilated cardiomyopathy prone to sustained ventricular arrhythmias.
Methods and Results: Forty-nine dilated cardiomyopathy patients were studied, 18 with a history of sustained ventricular tachycardia (  n = 6  ) or ventricular fibrillation (  n = 12  ) and 31 with no ventricular arrhythmias. The magnetocardiogram was registered and QT apex and QT end intervals were determined by a computer algorithm. Inhomogeneity of repolarization was characterized with indices describing QT apex and QT end dispersion, and T wave end duration. In addition, time-domain late fields of the QRS complex in magnetocardiography and QT dispersion in 12-lead ECG were determined. T wave end was longer in the arrhythmia group in patients with sinus rhythm (  87 ± 15 msec vs 73 ± 12 msec; P = 0.005  ) and in those not having bundle branch block. Magnetocardiographic late fields of the QRS complex were not different between groups. QT apex and end dispersion on magnetocardiography or 12-lead ECG showed no difference.
Conclusion: Prolongation of the end part of the T wave revealed by magnetocardiography is related to malignant ventricular arrhythmias in dilated cardiomyopathy. The results suggest that abnormal repolarization rather than delayed conduction underlies the arrhythmias in this disease.     

Genetic abnormalities responsible for dilated cardiomyopathy

Dilated cardiomyopathy (DCM), a disorder in which left ventricular dilation and dysfunction leads to congestive heart failure, is inherited in over 30% of cases. The underlying genetic mechanisms are slowly being unraveled, with multiple genes recently identified as causing DCM in some patients. The genes identified to date appear to encode proteins that either support the cytoskeleton or interact with the cytoskeleton. When mutated, these proteins destabilize the cardiomyocyte membrane or cytoskeleton via mechanical instability or force transduction causing poor cardiac systolic function and compensatory dilation. Once the entire group of genes causing DCM (genetic heterogeneity) are identified, improvements in diagnosis and treatment are expected.     

Familial dilated cardiomyopathy in patients transplanted for idiopathic dilated cardiomyopathy

OBJECTIVE: To evaluate the prevalence, clinical features, and pattern of inheritance of familial dilated cardiomyopathy (DCM) in heart transplant patients. PATIENTS AND METHOD: Patients with idiopathic DCM who had undergone heart transplantation were invited to participate. Patients with alcohol abuse were excluded. A clinical evaluation, 12-lead ECG, echocardiogram, blood tests, and DNA extraction were performed in patients and relatives. Familial DCM was defined as the presence of at least one relative with idiopathic DCM. Possible familial DCM was considered when at least one relative had left ventricular enlargement (LVE) (> 112% predicted LVEDD). RESULTS: One hundred and ninety-nine relatives of 43 families were studied. DCM was familial in 11 probands (25.6%) and possibly familial in 11 (25.6%). Fifteen relatives had DCM (7.5%), 26 (13.1%) LVE, and 5 (2.5%) hypertrophic cardiomyopathy. The pattern of inheritance was autosomal dominant in most families. Five probands (3 with familial DCM) had antecedents of consanguinity and possible recessive inheritance. Six probands (14%, 1 with familial DCM) had relatives with conduction system defects. Creatine kinase was moderately increased in 9 relatives (4.5%), 3 of them with LVE. Fifteen patients had at least moderate alcohol intake. Three of them had familial DCM (relatives without alcohol abuse) and 6 had possible familial DCM. CONCLUSIONS: The prevalence of familial DCM is high in patients who undergo heart transplant. Left ventricular enlargement, conduction system abnormalities, and elevated creatine kinase may be early markers of familial disease. Hypertrophic cardiomyopathy is present in some relatives of patients with idiopathic DCM. Familial DCM is present in patients with a previous diagnosis of alcoholic DCM.     

Relationships between segmental left ventricular wall motion abnormalities and pathological findings in patients with dilated cardiomyopathy

Relationships between segmental left ventricular wall motion abnormalities and myocardial fibrosis at autopsy were examined in 12 patients who died of dilated cardiomyopathy. In each case, wall motion abnormalities were assessed by two-dimensional echocardiograms for 11 segments, and semiquantitatively evaluated as normokinesis (N) to hypokinesis (H), severe hypokinesis (SH) or akinesis (A). From the necropsy specimens, the myocardial fibrosis ratio was histologically quantitated using a point-counting method in each segment corresponding to the echocardiographic segment. Wall motion abnormalities and the fibrosis ratio correlated significantly in a total of 132 segments of the 12 patients, but there were some discordances. The cases were then categorized in uniform and non-uniform groups based on the patterns of myocardial fibrosis. Wall motion abnormalities correlated much better with the fibrosis ratio in a total of 44 segments among four cases with non-uniform fibrosis, whereas no significant correlation was found in a total of 88 segments in eight cases with uniform fibrosis. The latter group had more severe segmental wall motion abnormalities in the interventricular septum than in the left ventricular free wall; and in the apical portion rather than in the basal portion, although no significant difference was observed in the fibrosis ratio among these regions. Patients with non-uniform fibrosis had higher incidences of chest pain and sudden deaths and a significantly larger left ventricular end-diastolic dimension on M-mode echocardiogram as compared to those with uniform fibrosis. Pathologically, in the former group, the heart was heavier, the mean left ventricular fibrosis ratio was significantly higher, and there was a greater incidence of infiltration of the myocardium by mononuclear cells, but there was no difference in the mean left ventricular wall thickness. These results suggest that myocardial fibrosis mainly contributes to the wall motion abnormalities in cases with non-uniform fibrosis which may be caused by chronic myocarditis, but not in cases with uniform fibrosis. In the latter group, other factors such as reduced contractility of the myocardial cells or lack of a compensatory mechanism for wall stress seem to play important roles in causing left ventricular wall motion abnormalities.     

Immunologic studies in patients with dilated cardiomyopathy]

In 10 cases of dilated cardiomyopathy the HLA-loci (A, B, C, DR) and marker expression on lymphocytes were studied. In this group the T4/T8-ratio was decreased and interleukin-2-expression was increased in relation to normals or patients with chronic coronary heart disease, respectively. 9 patients had the HLA-A1 or HLA-A2-locus in their siblings. In correlation analysis between immunological and hemodynamic parameters a good correlation of the number of NK-cells to the ejection fraction (r = 0.79) and negative correlation of helpercells (CD4) to the cardiac output were found (r = -0.80). The results of this attempt suggest an immunological pathogenesis of the dilated cardiomyopathy.     

Cardiac PPARalpha expression in patients with dilated cardiomyopathy

BACKGROUND: The peroxisome proliferator-activated receptor alpha (PPARalpha) is a central regulator of myocardial fatty acid (FA) metabolism implicated in the pathogenesis of heart failure. AIMS: To characterize PPARalpha regulation in human dilated cardiomyopathy (DCM), we studied the expression of cardiac PPARalpha, cardiac carnitine palmitoyl-transferase I (CPT-1), a major PPARalpha target gene, and of the cardiac glucose transporter GLUT-4 in patients with DCM. METHODS: Left ventricular biopsies were taken from patients with DCM (n=16) and control subjects (n=15), and mRNA expression was quantitated using real-time PCR (SYBR((R))Green) and protein expression was measured by Western immunoblotting. RESULTS: Left ventricular PPARalpha mRNA levels were significantly increased in the DCM group compared to the control group (136+/-25.4% vs. control, p<0.01). Consistently, DCM patients had a significantly higher cardiac CPT-1 mRNA expression (147+/-51% vs. control, p<0.05) compared to the control group. Cardiac GLUT-4 expression was similar in both groups. CONCLUSION: Elevated cardiac PPARalpha levels followed by an induction of cardiac CPT-1 expression may result in increased fatty acid metabolism for cardiac energy production in DCM, suggesting a specific cardiac metabolic program in human DCM compared to other types of cardiomyopathy.     

Functional and histopathologic correlation in patients with dilated cardiomyopathy: an integrated evaluation by multivariate analysis

To correlate left ventricular function and histologic features in patients with dilated cardiomyopathy, precise indexes of hemodynamics and semiquantitative histologic data were combined for multivariate analysis. Right endomyocardial biopsy was performed at the time of cardiac catheterization. Five hemodynamic indexes were used for functional assessment: ejection fraction, ratio of end-systolic stress to volume index, end-diastolic stress, time constant (T) of left ventricular pressure fall, and end-systolic stress. Six histologic findings (disarray of myofibers, hypertrophy of myofibers, scarcity of myofibrils, nuclear changes of myofibers, vacuolization of myofibers and proliferation of collagen fibers) were graded from (-) to (4+). Each finding was assigned to category (-) or (+) according to the absence or presence of significant abnormality. Ordinary statistical analysis revealed that, although ejection fraction was lower in category (+) for proliferation of collagen fibers, ratio of end-systolic to volume index was reduced for category (+) of hypertrophy of myofibers. A significant correlation was present between hypertrophy of myofibers and proliferation of collagen fibers by Spearman rank correlation. When principal component analysis was applied to the hemodynamic data, two principal components could be extracted. Fisher's discriminant analysis could clearly differentiate two categories (-) and (+) in the semiquantitative histologic finding of proliferation of collagen fibers. The analysis indicated that contractility was reduced with elevated afterload in that category (+). Thus, proliferation of collagen fibers may play a pivotal role in deteriorating contractility in patients with dilated cardiomyopathy.     

T-lymphocyte subsets in patients with idiopathic dilated cardiomyopathy

T-cell subsets were measured in the peripheral blood of 33 patients with heart failure from idiopathic dilated cardiomyopathy, 22 patients with heart failure from other causes, and 33 normal controls. Mean T-suppressor cell percentage was 30% in normals, 21% in patients with idiopathic dilated cardiomyopathy whose duration of symptoms was less than 1 year (P = 0.0005), and 26% in those with symptoms for greater than 1 year (P = 0.05). Similarly, percentage of T-suppressor cells in the group with heart failure from causes other than idiopathic dilated cardiomyopathy was significantly lower (23%; P = 0.005) in those with short duration of symptoms. When both heart failure groups were combined those with symptoms for less than 1 year had significantly lower T-suppressor frequencies (22%) than those with symptoms for more than 1 year (P = 0.015). Multivariate analysis identified duration of symptoms and age as the only independent predictors of T-suppressor cell frequencies. Decreased percentage of T-suppressor cells in patients with idiopathic dilated cardiomyopathy may be an epiphenomenon related to duration of heart failure. This should be taken into account in assigning an etiologic mechanism for T-suppressor cells in idiopathic dilated cardiomyopathy.     

Regional left ventricular wall motion abnormalities in idiopathic dilated cardiomyopathy

An evaluation and a comparison of left ventricular regional wall motion were performed in 32 patients with idiopathic dilated cardiomyopathy, none of whom had coronary artery diameter stenosis exceeding 20% in any major artery, and 17 control subjects, using frame by frame video intensity analysis of digitized ventriculograms. This technique evaluates the whole cardiac cycle in short overlapping intervals and yields information for systolic and diastolic events, without assumptions regarding the position and orientation of the ventricle. Diastolic regional wall motion abnormalities were found in 31 of 32 patients and systolic abnormalities were present in 16 patients. Asynchronous regions most commonly detected during diastole were anteroapical and apical; they were found in 19 of 32 patients. Regional contraction abnormality was observed in the apical and the anteroapical regions in 6 of 16 patients. Dilatation-induced changes in left ventricular shape exaggerate the phenomenon of higher wall stress at the apex of the normal ventricle. Basal wall motion is thus relatively preserved in dilated cardiomyopathy.     

PET abnormalities in patients with nonischemic cardiomyopathy

BACKGROUND: The abnormalities in dilated cardiomyopathy (DCM) are generally considered diffuse and to affect the left ventricle in a global manner. However, regional wall motion abnormalities and metabolic defects may also occur to varying, but unclear degrees. QRS width and metabolic defects on positron emission tomography (PET) correlate with survival. We sought to ascertain the prevalence of regional defects in DCM by multiple imaging modalities and to establish the relationship between QRS width and these defects. METHODS: In consecutive patients with advanced nonischemic DCM, undergoing cardiac transplant evaluation, we reviewed multiple imaging modalities (PET, 2-dimensional echocardiography, and radionuclide ventriculography) to quantify the incidence of regional metabolic and wall motion abnormalities and correlate them with clinical and electrocardiographic parameters. RESULTS: Of 44 patients studied, PET imaging revealed scar in 91% of patients, with a mean of 25 +/- 18% of the left ventricle involved, predominantly in the distribution of the left anterior descending artery. Regional wall motion abnormalities occurred in 51% of patients who underwent echocardiography and 59% of patients who underwent nuclear scintigraphy (with only 70% concordance). QRS duration on the surface electrocardiogram correlated positively with the degree of scarring (r=.52, P=.0007). CONCLUSIONS: The presence of scar (matched perfusion and metabolic defects) on PET scanning in patients with advanced DCM is not always indicative of coronary disease. Thus coronary angiography is usually required to define the etiology of systolic dysfunction. The extent of scar correlates with QRS duration. This may have implications for the application of cardiac resynchronization therapy.     

P-wave duration and P-wave dispersion in patients with dilated cardiomyopathy

BACKGROUND: P-wave dispersion (PWD) has been reported to be associated with inhomogeneous and discontinuous propagation of sinus impulses. In the present study, we aimed to investigate PWD in patients with dilated cardiomyopathy. METHOD: The study population consisted of 72 patients with dilated cardiomyopathy and 72 healthy control subjects. Left atrial diameter, left ventricular end-diastolic and end-systolic diameters and left ventricular ejection fraction of all patients and control subjects were measured by means of transthoracic echocardiography. Maximum P-wave duration (Pmaximum) and minimum P-wave duration (Pminimum) were measured from the 12-lead surface electrocardiogram. PWD was calculated as the difference between Pmaximum and Pminimum. RESULTS: Pmaximum and PWD of patients with dilated cardiomyopathy were significantly higher than those of control subjects (Pmaximum: 126+/-12 ms vs. 116+/-10 ms, PWD: 47+/-6 ms vs. 38+/-7 ms, respectively, P<0.001 for all). However, there was no statistically significant difference between patient group and control group regarding Pminimum (79+/-7 ms vs. 78+/-6 ms, respectively, P=0.27). Left atrial diameter was significantly higher in patients with dilated cardiomyopathy compared to control subjects (4.51+/-0.62 cm vs. 3.60+/-0.43 cm, respectively, P<0.001). Left ventricular ejection fraction was found to be significantly lower in patients with dilated cardiomyopathy compared to control subjects (33+/-5% vs. 63+/-7%, respectively, P<0.001). CONCLUSION: PWD was found to be significantly higher in patients with dilated cardiomyopathy than in healthy control subjects.     

Humoral immunity and lymphocyte subpopulations in patients with dilated cardiomyopathy

The incidence of serum organ and non-organ specific autoantibodies, the peripheral blood lymphocyte blastogenic response to phytohaemagglutinin, concanavalin A and pokeweek mitogen, and the surface markers of peripheral T and B lymphocytes were studied in 15 patients affected by coronary artery disease and in 21 patients with dilated cardiomyopathy. In the latter group there was a significantly impaired blastogenic response to concanavalin A with respect to both the normal control group and patients with coronary artery disease (P less than 0.01). The percentage of peripheral blood lymphocytes with cytotoxic/suppressor activity was also reduced in patients with dilated cardiomyopathy in comparison to normal subjects and patients with coronary artery disease (P less than 0.01 and P less than 0.05, respectively). These data may reflect an in vivo defect in suppressor cell function in patients with dilated cardiomyopathy.