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Ethnic and gender differences in electrocardiographic QT length and QT dispersion in hypertensive subjects
1The Peart-Rose Clinic and Departments of Clinical Pharmacology, Imperial College School of Medicine at St Mary's, St Mary's Hospital, London, UK. n.chapman@ic.ac.uk
Insights
This study found no significant ethnic or gender differences in QT parameters among hypertensive individuals. However, a trend suggested longer QT intervals in Black patients and female patients compared to White and male patients, respectively.
Area of Science:
- Cardiology
- Clinical Electrophysiology
- Hypertension Research
Background:
- Prolonged QT intervals and QT dispersion (QTd) are linked to adverse outcomes and mortality.
- In hypertensive individuals, QTd correlates with blood pressure (BP) and left ventricular mass index (LVMI).
- Existing data on QT parameters across ethnic groups, especially in hypertensives, is limited.
Purpose of the Study:
- To investigate ethnic and gender variations in QT parameters within a hypertensive population.
- To compare QT intervals and dispersion between Black and White hypertensive subjects, matched for key clinical factors.
- To examine gender differences in QT parameters among hypertensive individuals, controlling for age, race, BP, and left ventricular hypertrophy (LVH).
Main Methods:
- Selection of untreated hypertensive patients from a Hypertension Clinic database.
- Matching of Black and White subjects for age, sex, BP, and LVMI.
- Matching of male and female subjects for age, race, BP, and presence/absence of LVH.
- Measurement of maximum QT intervals (QTm), rate-corrected maximum QT intervals (QTc), and QT dispersion (QTd) from ECGs.
- Statistical analysis using Student's t-tests to identify group differences.
Main Results:
- No statistically significant ethnic or gender differences were observed in QT parameters.
- A trend indicated prolonged QTm and QTc in Black subjects compared to White subjects (P=0.08 and P=0.24, respectively).
- A trend suggested prolonged QTc in female subjects compared to male subjects (P=0.13).
Conclusions:
- In this cohort of matched hypertensive patients, no significant ethnic or gender disparities in QT parameters were found.
- Consistent with findings in normotensives, hypertensive females tended to have longer QTc intervals than males.
- The study did not confirm shorter QTc in Black hypertensives compared to White hypertensives, contrary to observations in US normotensives.
- Further research is needed to clarify ethnic differences in QT parameters between hypertensives and normotensives, and between US and UK Black populations.
- Prospective studies are required to determine if the prognostic significance of QT parameters varies across different gender and ethnic groups in hypertensive patients.
Background:
Prolonged QT intervals and/or increased QT dispersion (QTd) are associated with various pathological conditions and predict death in healthy individuals. Among hypertensives, QTd correlates with blood pressure (BP) and left ventricular mass index (LVMI) and QT intervals are prolonged in those with left ventricular hypertrophy (LVH). In normotensives, heart-rate corrected QT length (QTc) is longer in females than males, but QTd is greater in males than females. There are few data comparing QT parameters between different ethnic groups and none specifically in hypertensives. Among normotensives, compared with whites, QTc is reported to be shorter in African-Americans and longer in Chinese. We looked for ethnic and gender differences in QT parameters in hypertensive subjects.
Methods:
Untreated hypertensives were selected from a Hypertension Clinic database. Black and white subjects were matched for age, sex, BP and LVMI. Male and female subjects were matched for age, race, BP and the presence or absence of echocardiographic LVH. Maximum QT intervals (QTm), rate-corrected maximum QT intervals (QTc) and QT dispersion (QTd) were measured or calculated from ECGs. Data are presented as mean +/- s.d. Differences in QT parameters were sought between groups using Student's t-tests.
Results:
No ethnic or gender differences in QT parameters achieved statistical significance. However there was a tendency for QTm and QTc to be prolonged in blacks compared with whites (443 +/- 52 vs 421 +/- 47; P = 0.08 and 480 +/- 65 vs 463 +/- 40: P = 0.24 respectively), and for QTc to be prolonged in females compared with males (479 +/- 52 vs 461 +/- 45 ms; P= 0.13).
Conclusion:
In small groups of matched hypertensives, no ethnic or gender differences in QT parameters achieved statistical significance. However, similar to findings in normotensives, QTc tended to be longer in hypertensive females than males. In hypertensives, we failed to confirm the finding that QTc is shorter in blacks than whites, as seen in US normotensives. Whether this represents a difference between hypertensives and normotensives, or between US and UK blacks requires further investigation. Whether the prognostic significance of QT parameters in hypertensives differs between different gender and ethnic groups needs to be established from prospective studies. Journal of Human Hypertension (2000) 14, 403-405