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Left ventricular systolic function during stress echocardiography exercise in subjects with asymptomatic hereditary
Yukitaka Shizukuda1, Charles D Bolan, Dorothy J Tripodi
1Cardiovascular Branch, National Heart, Lung, and Blood Institute, National Institutes of Health, Bethesda, Maryland, USA. shizukuy@nhlbi.nih.gov
Insights
Asymptomatic individuals with hereditary hemochromatosis (HH) maintain normal left ventricular (LV) systolic function during exercise. Iron removal therapy did not alter stress echocardiography performance in these patients.
Area of Science:
- Cardiology
- Genetics
- Internal Medicine
Background:
- Hereditary hemochromatosis (HH) is a genetic disorder of iron overload.
- Left ventricular (LV) systolic function in asymptomatic HH patients is not well-understood.
- Stress echocardiography is a key tool for assessing cardiac function under stress.
Purpose of the Study:
- To evaluate left ventricular (LV) systolic function and stress echocardiography response in asymptomatic subjects with hereditary hemochromatosis (HH).
- To compare cardiac function between untreated HH, treated HH, and healthy controls.
- To assess the impact of iron removal therapy on cardiac function in HH patients.
Main Methods:
- Compared 43 asymptomatic HH patients (22 untreated, 21 treated) with 21 healthy controls.
- Assessed LV contractile reserve using continuous echocardiography and ECG during supine bicycle exercise.
- Nineteen untreated HH patients underwent repeat testing after 6 months of phlebotomy therapy.
Main Results:
- LV contractile reserve was preserved in asymptomatic HH patients at submaximal and peak exercise.
- No significant difference in LV ejection fraction response was observed between HH groups and controls.
- Abnormal ischemic stress ECG responses were more frequent in HH patients (33%) than controls (10%), likely false positives.
Conclusions:
- Left ventricular (LV) systolic function during exercise is preserved in asymptomatic hereditary hemochromatosis (HH) patients.
- Stress echocardiography performance is not affected by 6-month iron removal therapy via phlebotomy.
- Abnormal stress ECG findings in HH patients warrant further investigation to differentiate from true ischemia.
Abstract:
There is no information available on left ventricular (LV) systolic function and the response to stress echocardiography in asymptomatic subjects with hereditary hemochromatosis (HH). To evaluate this topic, 43 asymptomatic subjects with HH homozygous for the C282Y HFE gene mutation (22 untreated subjects [group A] and 21 long-term treated subjects [group B]) were compared with 21 age- and gender-matched normal volunteers negative for HFE mutations. Contractile reserve, as a measure of LV systolic function, was assessed using continuous echocardiographic imaging and electrocardiography during supine bicycle exercise. Nineteen subjects in group A had repeat tests after 6 months of induction phlebotomy therapy to assess the effect of iron removal. Exercise performance and hemodynamic variables of supine bicycle exercise were comparable between subjects with HH and controls. LV contractile reserve of asymptomatic subjects with HH was not impaired at either a 75-W submaximal exercise level (mean +/- SD difference in ejection fraction from baseline 13.8 +/- 6.2%, 11.5 +/- 6.8%, and 13.4 +/- 7.8% in groups A, B, and C, respectively; p = NS for all by analysis of variance) or at peak exercise (difference in ejection fraction from baseline 18.9 +/- 6.9%, 18.4 +/- 7.8%, and 20.3 +/- 8.1% in groups A, B, and C, respectively; p = NS for all by analysis of variance). However, the incidence of abnormal ischemic stress electrocardiographic responses was more frequent in subjects with HH as a whole (33%) compared with normal subjects (10%). Stress imaging revealed no regional wall motion abnormalities, suggesting that these were false-positive results. Iron removal by induction phlebotomy did not affect stress echocardiographic performance. In conclusion, LV systolic function during exercise in asymptomatic subjects with HH is preserved, and 6-month induction phlebotomy does not affect stress echocardiographic performance.
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