| Abstract: | The heterogeneity of individuals with blood pressure (BP) < 140/90 mmHg in terms of cardiovascular (CV) risk was reported as early as 1939 by Robinson and Brucer.1 BP in the range of 120–139/80–89 mmHg (labelled then as prehypertension) was observed to be associated with high risk of progression to hypertension (HT) and cardiovascular disease (CVD) later in life when compared with BP < 120/80 mm Hg.1The term prehypertension was adopted in May 2003 by the Seventh Report of the Joint National Committee on Prevention, Detection, Evaluation and Treatment of High blood Pressure (JNC-7) to describe BP range of 120–139/80–89 mmHg.2 The resuscitation of this terminology/concept in JNC-7 was a sequel to the documentation of a higher morbidity in individuals with prehypertension in landmark publications.3-5 Prehypertension (PHT) was defined in JNC-7 not only to emphasise the excess risk associated with BP in this range, but also to focus increased clinical and public health attention on prevention.2,6,7Prevalence rates of PHT among adults in the United States, Ghana and northern Nigeria have been reported to be 31, 40 and 58.7%, respectively.7-9 In most studies, including the ones above, PHT was more prevalent than hypertension.7-9 Though PHT is associated with increased risk of major CV events independently of other CV risk factors,10 most individuals (90%) with PHT have at least one cardiovascular risk factor such as dyslipidaemia, abdominal obesity, hyperinsulinaemia, impaired fasting glucose levels, insulin resistance, a prothrombotic state, tobacco use, endothelial dysfunction, and impaired vascular distensibility.6,7,9,10QT interval dispersion (QTd) (the difference between the longest and the shortest QT intervals on a surface ECG), when excessive, is associated with increased risk of cardiovascular morbidity and mortality in population studies, and many clinical conditions, including hypertension.11,12 This has been related to ventricular electrical instability, providing the necessary substrate for lethal ventricular arrhythmias.12,13 Greater QTd and left ventricular mass have been demonstrated in hypertensive individuals compared with normal individuals.11,13,14Considering the well-established, linear relationship between BP and the risk of cardiovascular events, the CV risk associated with PHT is intermediate between normotension and hypertension.2,03 Hence, electrocardiographic and echocardiographic indices of target-organ damage in PHT may also be intermediate between normotension and hypertension. The aims of this study were: (1) to compare the QTd and indices of left ventricular hypertrophy in adult black normal and prehypertensive subjects, and (2) to evaluate the relationship of QTd with electrocardiographic and echocardiographic indices in these subjects. |
