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Exercise blood pressure and echocardiographic abnormalities in genetically comparable populations
B J Naimark1, J Axelsson, S B Sigurdsson
1Department of Physiology, Faculty of Medicine, University of Manitoba, Winnipeg.
Objective:
To determine the relationship between the systolic blood pressure response to exercise and the echocardiographic dimensions of the left atrium and ventricle in two geographically separate, but genetically comparable, populations.
Design And Setting:
The study was cross-sectional. The settings were two semirural communities, one in Iceland and one in Manitoba.
Subjects:
Individuals from families where there had been no intermarriage with non-Icelandic individuals were eligible. Of the 200 eligible men in Manitoba and the 150 men in Iceland, 157 and 121 men, respectively, agreed to participate. In the majority of cases, those who chose not to participate stated that work commitments prevented them from taking part. The subjects were aged 25 to 63 years and had blood pressure less than 160/95 mmHg at rest.
Interventions:
Blood pressure was taken at rest and during standardized bicycle ergometry. Left ventricular and atrial echocardiography was performed on a selected number of subjects.
Main Results:
The Canadians of 'pure' Icelandic descent had a higher prevalence of exaggerated exercise systolic blood pressure (ESBP), left atrial enlargement (LAE) and left ventricular hypertrophy (LVH) than native Icelanders. Given their genetic similarity, it is suggested that the difference between the two groups is due to environmental factors. Within each group, subjects with exaggerated ESBP had a significantly greater left atrial dimension index and left ventricular mass index than subjects without an exaggerated ESBP. The relationship of ESBP with left atrial dimension index and left ventricular mass index was independent of age, body mass index and resting blood pressure. LVH was of the eccentric type and was absent in the majority of cases with LAE; however, LAE was present in nearly all LVH cases.
Conclusions:
This study demonstrates that an exaggerated ESBP in individuals with resting blood pressure less than 160/95 mmHg is not an innocuous finding it is associated with demonstrable cardiac abnormalities (LAE and LVH). Furthermore, it is proposed that the presence of LAE, with or without LVH, may add to the value of an exaggerated ESBP in identifying individuals at increased risk of developing sustained resting essential hypertension.