Sense and sensibility

Sphygmomanometry and electrocardiography (ECG) are fundamental tools in cardiovascular medicine since more than 100 years. They are manifested by their specious simplicity and their proven value in large scale epidemiological observations for numerous indications e.g. left ventricular hypertrophy (LVH). Based thereupon new sensors and concepts like echocardiography (ECHO) or central blood pressure (CBP), designed to increase sensitivity and/or specificity, evolved. In the last 10 years, the superiority of central over peripheral arterial hemodynamics has been repeatedly documented and recently summarized.¹ Additionally the role of left ventricular hypertrophy as a measure of hypertensive end-organ damage and as independent predictor of outcome has been emphasized in major guidelines.² The relationship between CBP and LVH has also been well described,³ again with central pressures being closer associated with left ventricular wall thickness and mass than peripheral pressures.

Typically in studies of this kind, echocardiography was used for assessment of left ventricular mass. In clinical routine, electrocardiography often is the first method to diagnose LVH, and major outcome trials have included patients with LVH on the basis of ECG-criteria rather than echocardiograms.⁴ In general ECG is less sensitive compared to ECHO, but highly specific in diagnosing LVH. Surprisingly the relationship between CBP and LVH characterized by ECG has not been investigated so far. Wohlfahrt and colleagues have started to fill this gap. In their actual study⁵ on the relation of CBP and ECG-LVH, they showed that non invasively determined CBP in subjects over 45 years is stronger related to ECG-LVH than brachial blood pressure, further supporting the concept of the superiority of central pressures.

On the other hand, the authors did not find such a relationship in persons younger than 45 years. This raises some issues to be addressed:

• 1) ECG-LVH was present in roughly 10% of mainly young men with low blood pressures and a low prevalence of hypertension. Most likely, factors other than blood pressure may have accounted for LVH in this group of individuals. The authors discuss, whether Sokolow Index is reliable in this population. In addition, it may be speculated that for some of these individuals LVH indeed may have been present, but due to other reasons than hypertension, e.g. the more physiological ‘athletes heart’ or more pathological forms like hypertrophic cardiomyopathy. However, we have no information on this subject from the published data, and clearly echocardiography or cardiac MRI would be needed to clarify this issue.

• 2) In the older age group, use of medication may have weakened the relationship between LVH and CBP. Of note, in the group with LVH almost 30% used betablockers, which have a weaker effect on LV mass and CPB than other antihypertensives. Although the authors tried to account for this in multivariate analysis, a study in untreated subjects may be of value.

• 3) As stated in the study, BP was measured only at one single occasion during the study. It is likely that an increase in BP measurements, for example using ambulatory blood pressure measurement, would have led to closer associations. Due to technological progress the assessment of CBP during ambulatory blood pressure measurement seems possible now.^{6, 7}

There is still fragmentation in the mosaic that describes the relation between left ventricular structure (and function) and CBP. Wohlfahrt and colleagues brought in an overdue piece of information to this picture.