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Parasympathetic dysfunction in hypertrophic cardiomyopathy assessed by heart rate variability: comparison between short-term and 24-h measurements
Umeå University, Faculty of Medicine, Department of Public Health and Clinical Medicine, Medicine.
Umeå University, Faculty of Medicine, Department of Radiation Sciences.
Umeå University, Faculty of Medicine, Department of Public Health and Clinical Medicine, Medicine.
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2005 (English)In: Clinical Physiology and Functional Imaging, ISSN 1475-0961, E-ISSN 1475-097X, Vol. 25, no 2, 90-99 p.Article in journal (Other academic) Published
Abstract [en]

In this study, we evaluate cardiac autonomic function in hypertrophic cardiomyopathy (HCM) by assessing heart rate variability (HRV), comparing a short-term laboratory method with an ambulatory (24-h) method, in patients with and without beta-blockade. Reduced HRV is a risk factor for adverse events in some cardiac diseases, but is not a proven risk indicator in HCM. Analysis of HRV has been based on either short- or long-term electrocardiographic recordings and previous studies in HCM have shown conflicting results. There is no consensus on which method to prefer, and we evaluate, for the first time, both short- and long-term analyses in patients with HCM. Long- and short-term HRV analyses were performed in 43 patients with HCM. They were divided in two groups, 22 patients on beta-blockade and 21 non-treated patients. As controls, 121 healthy subjects were used. Young patients without beta-blockade showed a reduction in HRV parameters reflecting parasympathetic function, both in the short- and long-term registrations, which was attenuated by beta-blockade. Parasympathetic autonomic regulation was found to be impaired in young patients with HCM. This may be of clinical relevance as abnormal autonomic function might be a substrate for malignant dysrhythmias. The impairment was attenuated by beta-blockade, which might indicate a clinically useful effect. We also show that short- and long-term methods yield similar results, suggesting that a short-term registration might be sufficient to assess HRV in patients with HCM.

Place, publisher, year, edition, pages
2005. Vol. 25, no 2, 90-99 p.
Keyword [en]
Autonomic nervous system, cross-sectional study, heart rate variability, hypertrophic cardiomyopathy
National Category
Medical and Health Sciences
URN: urn:nbn:se:umu:diva-14178DOI: 10.1111/j.1475-097X.2004.00595.xPubMedID: 15725307OAI: diva2:153849
Available from: 2007-04-20 Created: 2007-04-20 Last updated: 2010-08-10Bibliographically approved
In thesis
1. Hypertrophic cardiomyopathy in Northern Sweden: with special emphasis on molecular genetics
Open this publication in new window or tab >>Hypertrophic cardiomyopathy in Northern Sweden: with special emphasis on molecular genetics
2004 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Hypertrophic cardiomyopathy (HCM) is a heterogeneous, often familial disease, characterized by cardiac hypertrophy, predominantly affecting the interventricular septum. To date, no study has systematically analysed the genetic and phenotypic aspects of the disease in a Swedish population. The aim of this thesis was to identify the genotypes causing HCM in northern Sweden, to characterize the disease phenotypes and correlate these findings.

Forty-six patients were recruited for the genetic studies (21 women), 11 familial and 35 sporadic cases. Eight sarcomeric protein genes were screened for mutations. A total of 11 different disease causing mutations were found in four genes. Six of the mutations were previously not described. A novel mutation (a 33 base pair deletion) in the troponin I gene was found in one HCM family. Despite the severe genetic defect, the associated phenotype displayed only mild cardiac hypertrophy and few symptoms. Most mutations (64%) were identified in the myosin binding protein C gene, a gene considered to have a low penetrance. Mutations were identified in 10 of 11 familial HCM cases, but only in three of the 35 sporadic cases.

It was found that cardiac amyloidosis can sometimes present itself as HCM. Three HCM patients (7%) carried the ATTR Val30Met mutation, also found in Swedish patients with familial amyloid polyneuropathy (FAP). The patients had no symptoms of polyneuropathy, but cardiac amyloidosis as the cause of hypertrophy was verified by myocardial biopsy in an index case. Amyloid heart disease should therefore be considered as a differential diagnosis in patients with HCM.

By studying heart rate variability (HRV), it was found that young patients with HCM had signs of autonomic dysfunction, expressed as a reduced HRV. Treatment with beta-blockade attenuated these effects. Abnormal autonomic function might be a substrate for lethal arrhythmias, most often encountered in younger patients with HCM. The results suggest a possible protective effect of beta-blockade, remaining to be studied further.

Ventricular function is frequently abnormal in HCM. In particular, diastolic dysfunction has been demonstrated. The recently described myocardial performance index allows the assessment of cardiac function by combining systolic and diastolic performance. We found that patients with hypertrophic cardiomyopathy had evidence of global and regional right ventricular dysfunction, besides left ventricular dysfunction. Hypertrophic cardiomyopathy is traditionally considered to be a disease of the left ventricle. The results show that hypertrophic cardiomyopathy should more be regarded as a biventricular disease.

In conclusion, the myosin binding protein C gene is the most common gene causing familial HCM in northern Sweden. This disease gene is considered to be associated with a mild, late-onset disease with ≈50% penetrance at 30 years of age. The low disease penetrance emphasizes the importance of adequate family screening when evaluating patients with HCM, since the familial nature of the disease might easily be overlooked. These particular disease features in northern Sweden contrast to most previous reports, which indicate another disease gene as the most frequent in HCM, associated with a much higher penetrance. Amyloid heart disease, requiring different treatment than HCM, should be kept in mind as a differential diagnosis in the management of patients with HCM.

Key words: Hypertrophic cardiomyopathy, genetics, autonomic nervous system, familial amyloid polyneuropathy, echocardiography.

Umeå University medical dissertations, ISSN 0346-6612 ; 894
Hypertrophic cardiomyopathy, genetics, autonomic nervous system, familial amyloid polyneuropathy, echocardiography
Research subject
urn:nbn:se:umu:diva-274 (URN)91-7305-660-X (ISBN)
Public defence
2004-05-28, Sal E04, Byggnad 6E, Norrlands Universitetssjukhus, Umeå, 09:00 (English)
Available from: 2004-05-10 Created: 2004-05-10 Last updated: 2010-08-10Bibliographically approved

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