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Sunday, March 19, 2017

Do low levels of cardiovascular fitness predispose to cardiac hypertrophy?

 There is evidence  that suggests low levels of cardiac fitness predispose to maladaptive cardiac remodeling  typically manifest as concentric remodeling and concentric hypertrophy and increased ventricular stiffness and diastolic dysfunction.

Lovic and Kokkinos and co workers correctly point out that the cardiac hypertrophy consequent to  high blood pressure differs from the typical physiological cardiac hypertrophy of the endurance athlete realizing that  extreme examples of the latter can be difficult to distinguish from the former.

Lovic et al  makes the following  argument in a 2016 issue of the Journal of Hypertension.

Low fitness level individuals will reach a systolic blood  pressure of 150 at low levels of exercise, e.g. 4-5 METS , which are  levels commonly encountered in some activities  of everyday living.
150 systolic  blood pressure is necessary to trigger cardiac remodeling. Individuals, who are more fit, are able to do that level of work without that degree of BP rise. So individuals with low fitness may spend considerable  time each day with a BP of sufficient magnitude to trigger hypertrophic changes in  the left ventricle. even though their BP as measured in their doctor's office may be normal.

Their data (1) found an inverse relationship between exercise capacity, blood pressure response to exercise and  left ventricular mass.Futher they have published data that showed 16 weeks of aerobic training resulted in subjects having  a significantly lower blood pressure  level when they  exercised at the every day activity level of 3-5 METS. A reduction in previously elevated left ventricular mass was also shown.

Other data consistent  with this notion comes from a study by Brinker et al ( 2) from Southwestern Medical School in Dallas. They studied subjects aged 42 -67 years of age with stress testing and echocardiography. Those individuals in the lowest fitness category ( they divided the group into 3 fitness levels ) had 40 % concentric hypertrophy as well as a 9% prevalence of diastolic dysfunction ( as defined  by the e/a ratio on mitral valve echo flow studies)

Data from the Dallas group and others have outlined the concept of there being two distinct cardiac phenotypes related to the development of both heart failure with reduced ejection fraction (HFrEF) and heart failure with preserved ejection fraction (HFpEF).They are:

1)Subclinical systolic dysfunction (EF may be normal but abnormalities detectable by measurement of global strain with speckle echocardiography)),with eccentric cardiac hypertrophy with increased LV diameter)-the proposed precursor to HFrEF

2)Subclinical diastolic dysfunction with concentric LV hypertrophy; with increased relative wall thickness (RWT) -the proposed precursor to diastolic heart failure (HFpEF)

Increasing data strongly suggest that low fitness levels predispose to the precursors of HFpEF.
Lovic's work suggesting that exercise induced elevated blood pressure in the unfit may be one possible mechanism involved.



1)Lovic, D et al Left ventricular hypertrophy in athletes and hypertensive patients.J Clin Hypertension 2017,

2) Brinker SK et al. An association of Cardiorespiratory Fitness with left ventricular remodeling and diastolic dysfunction. JACC Heart Failure., Vol 2, no 3, 2014, p 238


5/1/17 An embarrassingly large number of typos and misspellings were corrected and again on 5/16/17.

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