New theories. Causes of dilated cardiomyopathy

[Molecular mechanisms of genetic damages of the myocardium in cardiomyopathy]

The review highlighted problems of reorganization of myocardical contractile and cytoskeletal proteins in cardiomyopathy (CM). The role of the genetic factors coding contractile proteins, proteins of thin and thick filaments, and also extracellular matrix proteins in processes of formation and development of hypertrophic (HCM) and dilated (DCM) cardiomyopathy are analyzed. The mechanisms responsible for the changes in cardiac proteins on regulation involved into force generation, its transfer, recycling ATP, impairments in transmembranal signals, that finally lead to cardiac cell dysfunction determining various manifestations of CM are considered.

Sixty-four-slice multidetector computed tomography: an accurate imaging modality for the evaluation of coronary arteries in dilated cardiomyopathy of unknown etiology

BACKGROUND

The goal of this study was to assess the safety, feasibility, and diagnostic accuracy of 64-slice multidetector computed tomography (MDCT) for the evaluation of coronary arteries in dilated cardiomyopathy (DCM) of unknown etiology. Sixteen-slice MDCT is useful in patients affected by DCM. However, technical limitations, such as cardiac arrhythmias, an inability of patients to sustain a long breath-hold, and the need of a high dose of contrast agent may limit its accuracy and widespread use.

METHODS AND RESULTS

Invasive coronary angiography (ICA) and MDCT coronary angiography were performed on 132 consecutive patients (82 men; age 63+/-11 years) affected by DCM (ejection fraction, 34+/-10%) of unknown etiology. In 2 patients (1.5%), MDCT was not feasible because of atrial fibrillation. Of the remaining 130 patients, 88 exhibited normal and 42 exhibited diseased coronary arteries in both MDCT and ICA. All patients with coronary artery disease except for 1 were correctly classified by MDCT as 1-vessel (11 cases), 2-vessel (13 cases), and 3-vessel (18 cases) disease. In the segment-based analyses, the overall feasibility for MDCT was 98.5% (1902 of 1930 segments). Segment-based and patient-based analyses for the detection of luminal stenosis of >50% and >70% were performed. The sensitivity, specificity, positive predictive value, negative predictive value, and accuracy of MDCT for the detection of >50% stenosis were 98.1%, 99.9%, 98.7%, 99.8%, and 99.7%, respectively. The sensitivity, specificity, positive predictive value, negative predictive value, and accuracy of MDCT for the detection of >70% stenosis were 99.5%, 98.6%, 94.1%, 99.9%, and 99.4%, respectively.

CONCLUSIONS

Excellent feasibility and diagnostic accuracy, combined with low invasiveness, make 64-slice MDCT an ideal imaging modality for the anatomic evaluation of coronary circulation in patients with DCM of unknown etiology.

Diagnostic accuracy of multidetector computed tomography coronary angiography in patients with dilated cardiomyopathy

OBJECTIVES

The purpose of this work was to assess the safety, feasibility, and diagnostic accuracy of multidetector computed tomography (MDCT) in dilated cardiomyopathy (DCM) of unknown etiology.

BACKGROUND

Multidetector computed tomography is an appropriate noninvasive tool for coronary artery disease (CAD) detection, particularly in patients with low probability of the disease, such as patients with DCM of unknown origin.

METHODS

We studied 61 unknown origin DCM patients (ejection fraction: 33.9 +/- 8.6%, group 1) and 139 patients with normal cardiac function with indications for coronary angiography (group 2, control population). All underwent coronary MDCT and angiography. Multidetector computed tomography images were acquired by light speed 16-slice computed tomography. The degree of stenosis was estimated in 15 coronary artery segments according to the American Heart Association model.

RESULTS

In group 1, no MDCT-related complications were found, while 10 complications were associated with conventional angiography (p = 0.001). Overall feasibility of coronary artery visualization was 97.2% (863 of 888 segments). The most frequent cause of artifacts was interference from a hypertrophic cardiac venous system (10 artifacts, 40%). In group 2, overall feasibility was 96.1% (p = NS vs. group 1). In group 1, all cases with normal (44 cases) or pathological (17 cases) coronary arteries by conventional coronary angiography were correctly detected by MDCT, with, in 1 case, disparity of stenosis severity. In group 1, sensitivity, specificity, and positive and negative predictive values of MDCT for the identification of >50% stenosis were 99%, 96.2%, 81.2%, and 99.8%, respectively. In group 2, sensitivity and negative predictive values were lower than in group 1 (86.1% vs. 99% and 96.4% vs. 99.8%, respectively); specificity (96.4%) and positive predictive value (86.1%) were not significantly different versus group 1.

CONCLUSIONS

Multidetector computed tomography is feasible, safe, and accurate for identification of idiopathic versus ischemic DCM, and may represent an alternative to coronary angiography.

Role of the sarcoplasmic reticulum in altered action potential and contraction of myopathic human and hamster ventricle

1. The present experiments were performed in order to study the role of the sarcoplasmic reticulum (SR) in the altered action potential and contraction of ventricular myocardium obtained from myopathic Syrian hamster and explanted human hearts (n = 8). The hamsters included age-matched healthy hamsters (F1B; n = 18), young myopathic hamsters (Bio 14.6; n = 8; aged 17-27 weeks) and older myopathic hamsters (n = 10; aged 39-43 weeks). 2. Action potentials were recorded by means of a microelectrode technique and force was recorded using a transducer. Post-rest potentiation of contraction (PRPC), a measure of the SR Ca2+-pumping activity, was determined after different rest intervals (2-60 s). Furthermore, cyclopiazonic acid (10 micro mol/L), a specific blocker of SR Ca2+-ATPase, was used to unmask abnormalities in the function of the SR. 3. The relationship between PRPC and rest interval was similar in younger healthy and myopathic hamsters, but the curve of the older myopathic muscle was obviously shifted downwards. Cyclopiazonic acid decreased predominantly the ascending part of the curve in both the healthy and myopathic hamster myocardium and could induce spontaneous action potentials during drug exposure or after washout. 4. In human myopathic myocardium, the curve of the PRPC-rest interval peaked at longer intervals (40-60 s) compared with that of the hamsters (10-20 s). Cyclopiazonic acid markedly depressed the relationship and increased the diastolic force (contracture) at high driving frequency, but did not induce action potentials during the rest interval. 5. We conclude that an impaired function of the SR contributes to the progressive deterioration of ventricular function in dilated cardiomyopathy and that the electromechanical behaviour of the ventricular myocardium of patients affected by dilated cardiomyopathy shows similarity and differences with the myopathic Syrian hamster model.