CARDIAC FUNCTION IN PRIMARY MYOCARDIAL DISORDERS II

High validity of cardiomyopathy diagnoses in western Sweden (1989-2009)

Aim

Hospital discharges with a diagnosis of cardiomyopathy have more than doubled in Sweden since 1987. We validated the cardiomyopathy diagnoses over this time period to investigate that the increase was real and not a result of improved recognition of the diagnosis and better diagnostic methods.

Methods and results

Every fifth year from 1989 to 2009, records for all patients with a cardiomyopathy diagnosis were identified by searching the local registers in three hospitals in Västra Götaland, Sweden. The diagnoses were validated according to criteria defined by the European Society of Cardiology from 2008. The population comprised 611 cases with cardiomyopathy diagnoses [mean age 58.9 (SD 15.5) years, 68.2% male], divided into three major groups: dilated, hypertrophic, and other cardiomyopathies. Hypertrophic cardiomyopathy and hypertrophic obstructive cardiomyopathy were analysed as a group. Cardiomyopathies for which there were few cases, such as restrictive, arrhythmogenic right ventricular, left ventricular non‐compaction, takotsubo, and peripartum cardiomyopathies, were analysed together and defined as ‘other cardiomyopathies’. Relevant co‐morbidities were registered. The use of echocardiography was 99.7%, of which 94.6% was complete echocardiography reports. The accuracy rates of the diagnoses dilated cardiomyopathy, hypertrophic cardiomyopathy, and other cardiomyopathies were 85.5%, 87.5%, and 100%, respectively, with no differences between the three hospitals or years studied; nor did the prevalence of co‐morbidities differ.

Conclusions

The accuracy rate of the cardiomyopathy diagnoses from in‐hospital records from >600 patients in western Sweden during a 20 year period was 86.6%, with no significant trend over time, strengthening epidemiological findings that this is likely due to an actual increase in cardiomyopathy diagnoses rather than changes in coding practices. The use of echocardiography was high, and there was no significant difference in co‐morbidities during the study period. The accuracy rate of the cardiomyopathy diagnoses during the 20 year period was high. The use of diagnostic tools did not increase under the study period, and once cardiomyopathy diagnoses were suspected, echocardiography was performed in almost all cases. In this study, the occurrence of cardiomyopathy was increasing over time without significant increase of co‐morbidity, supporting that an actual increase of cardiomyopathy has occurred.

Idiopathic Dilated Cardiomyopathy as a Late Complication of Healed Viral (Coxsackie B virus) Myocarditis: Historical Analysis, Review of the Lliterature, and a Postulated Unifying Hypothesis

A historically based literature review of the relationship between acute viral myocarditis and the subsequent development of a dilated cardiomyopathic state is presented. A strong emphasis on a state of definitional ambiguity in the literature as regards the timing of the myopathic state following a viral infection is noted, i.e. does the myopathic state develop acutely and concomitantly with viral myocarditis due to overwhelming viral mediated myocardial cell necrosis, subacutely due to negative remodeling following severe but not overwhelming viral mediated myocardial cell necrosis, subacutely due to a sustained immune mediated myocarditis or in a delayed time frame following complete recovery from the initial infection (i.e. a return of normal histology and the absence of any cellular infiltrate and the presence of normal cardiac function). Evidence for the first two mechanisms is supported by the literature; evidence for the immune mediated chronic myocarditis remains controversial while hard evidence for the development of an idiopathic dilated cardiomyopathy (IDCM) as a late downstream complication following complete recovery from a bout of myocarditis is nonexistent. Recent basic virologic studies of myocarditis and the potential effects of retained noninfectious viral genomic material within the myocardium are reviewed. These studies allow for the proposal of a hypothetical mechanism whereby IDCM develops as a downstream complication of acute viral myocarditis.

Familial dilated cardiomyopathy: a worse prognosis compared with sporadic forms

OBJECTIVE

To establish the time of onset of dilated cardiomyopathy (DCM) by review of annual chest x rays, which are obligatory in Hungary.

DESIGN

A retrospective survey of chest x rays of a cohort of confirmed cases of DCM, to assess time of onset of cardiomegaly. Clinical course was compared by follow up over a mean of six years from the time of diagnosis.

SUBJECTS

240 patients with DCM (31 familial, 209 non-familial). Diagnosis was made by echocardiography in all cases and confirmed by coronary angiography and heart biopsy in some cases.

MAIN RESULTS

At diagnosis, the mean age of the patients was 31.8 years in the familial group and 39.6 years in the non-familial group (P < 0.05). The time between the onset of cardiomegaly (cardiothoracic ratio > 0.45) and clinical diagnosis was 8.0 and 10.1 years respectively (P < 0.05). The six year survival was 6% in the familial group and 23% in the non-familial group (P < 0.05).

CONCLUSIONS

The familial form of DCM is the more malignant form: it occurs at an earlier age and progresses more rapidly than non-familial DCM.

Myocardial fiber diameter and regional distribution in the ventricular wall of normal adult hearts, hypertensive hearts and hearts with hypertrophic cardiomyopathy

Myocardial fiber diameters were measured to determine their distribution throughout the ventricular wall in normal adult hearts, hypertensive hearts and hearts with hypertrophic cardiomyopathy (HCM). In normal adult hearts and hypertensive hearts, the diameter decreased from the inner to the outer third of the left ventricular free wall and from the left ventricular side to the right ventricular side of the septum. In HCM, these regional differences were preserved in the left ventricular free wall, but not in the septum. The diameter was greatest in the middle third of the septum, where myocardial fiber disarray was widely distributed. The diameters of the fibers in the right ventricular side of the septum were significantly larger than those of the fibers in the left ventricular side of the septum in HCM. This finding, in contrast to that in normal adult hearts or hypertensive hearts, was considered to be related to the inward convex curvature of the left ventricular chamber. Although there was no significant difference in the diameter of myocardial fibers in the left ventricular free wall between hypertensive hearts and hearts with HCM, the diameters of those in the right ventricular free wall, in the right ventricular side of the septum and in the middle third of the septum were significantly larger in HCM than in hypertensive hearts. We conclude that there is a transmural variation of myocardial fiber diameter in the left ventricular free wall and the ventricular septum, and such transmural variation in HCM is clearly different from that in hypertensive hearts.

The frontiers of cardiomyopathy

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The clinical course of primary myocardial disease in infants and children

A total of 161 infants and children, ranging in age from 1 day to 17 years at initial encounter (mean, 3.7 years), was seen over a 30 year period with primary myocardial disease (idiopathic myocarditis, nonobstructive cardiomyopathy, endocardial fibroelastosis, and an anatomically unknown category). These patients were observed from 1 hour to 23 years after initial encounter and cardiac disease has resolved in 27 per cent, resulted in death in 35 per cent, and continues in 38 per cent. The majority were first referred to us with congestive heart failure; all exhibited ST-T changes and cardiomegaly, 67 of 150 had left ventricular hypertrophy, 23 of 151 arrhythmias, and 55 of 153 pulmonary vascular congestion. Initial ventricular depolarization abnormalities were very frequent. Significant clinical predictors of fatal outcome included pulmonary vascular congestion, "northwest" axis deviation, and a cardiac index less than three L./min./M.2. Death occurred during the first year after initial encounter in 44 of 57 who died, and in all 13 with proved myocarditis. Primary myocardial disease is a serious disease of infancy and childhood, resulting in death or residual cardiac disease in three fourths of those affected.

Mechanism of left ventricular outlfow obstruction in patients with obstructive asymmetric septal hypertrophy (idiopathic hypertrophic subaortic stenosis)

Left ventricular outflow obstruction in patients with idiopathic hypertrophic subaortic stenosis or obstructive asymmetric septal hypertrophy is due to abnormal forward motion during systole of the anterior mitral leaflet. To determine why some patients with this disease hav left ventricular outflow obstruction whereas others do not, we studied a large number of patiens with assymetric septal hypertrophy using both one- and two-dimensional echocardiography. In 100 patients with asymmetric septal hypertrophy and 22 normal subjects, mitral valve position at the onset of systole was quantitated by measuring the distance from the ventricular septum to the mitral valve and the distance from the mitral valve to the posterior left ventricular wall. None of the normal subjects and only 3 (6 percent) of 51 patients with nonobstructive asymmetric septal hypertrophy had a septal-mitral valve distance of less than 20 mm compared with 23 (66 percent) of 35 patients with obstructive asymmetric septal hypertrophy. Moreover, the mitral valve at the onset of systole was actually positioned forward in the left ventricular activity. Two-dimensional studies in 11 patients with obstructive asymmetric septal hypertrophy revealed that contraction of the malaligned papillary muscles did not cause the abnormal forward mitral valve motion. We propose that the left ventricular outflow obstruction in patients with obstructive asymmetric septal hypertrophy occurs as a result of two factors: (1) narrowing of the left ventricular outflow tract at the onset of systole, and (2) hydrodynamic forces generated by contraction on the left ventricle.

Cardiovascular effects of methylmethacrylate cement

Experiments were carried out on dogs in an attempt to identify the mechanisms underlying the systemic hypotension associated with the application of acrylic cement substances to raw bone surfaces, as in reconstructive hip surgery. Intravenous injection of the liquid component of such cements (monomeric methylmethacrylate) into six dogs produced a significant fall in blood pressure together with an increase in heart rate and cardiac output. This seemed to be due to peripheral vasodilatation caused directly by the monomer and not through the release of histamine. Absorption of free monomer from the mixed cement into the systemic circulation at operation is likely to have the same effect. Precautionary measures can be taken and groups of patients who are especially at risk can be identified, thus reducing the hazards of total hip replacement.

Heart failure from unexplained cardiomyopathy

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