Fifty years of cardiac catheterisation in the differential diagnosis of left ventricular outflow tract obstruction: the Brockenbrough, Braunwald sign.

Editor

In February 1961, Brockenbrough, Braunwald and Morrow described a new haemodynamic test in the differential diagnosis of left ventricular outflow tract (LVOT) obstruction, based on the haemodynamic profiles of the left ventricle and aorta immediately following an extrasystolic beat1. Despite 50 years of multiple technological advances, the observation retains a place in the discrimination of fixed versus dynamic LVOT obstruction.

A 59 year old man, with hypertrophic cardiomyopathy was admitted for cardiac catheterisation after recent echocardiographic examination had shown a rise in LVOT gradient with progression of symptoms.

Simultaneous left ventricular and aortic pressure tracings revealed a classical Brockenbrough-Braunwald sign (figure 1) in keeping with “dynamic” LVOT obstruction. The sign is characterised by an abrupt increase in peak-systolic LVOT gradient, coupled with a decrease in aortic pulse pressure, immediately after an extrasystolic beat. It is distinct from “fixed” obstruction (e.g. aortic stenosis) where both the aortic pulse pressure and LV systolic pressure increase following an extrasystolic beat (figure 2).

Fig 1

Dynamic left ventricular outflow tract (LVOT) obstruction (the Brockenbrough-Braunwald sign). At rest, a small (10mmHg) LVOT gradient is present (a) with an aortic pulse pressure of 110mmHg (b). Following two extrasystolic beats (VPC) there is a marked increase in LVOT gradient to 105mmHg (A) with a corresponding fall in pulse pressure to 75mmHg (B).

Fig 2

Fixed left ventricular outflow tract (LVOT) obstruction (In this example, aortic stenosis from the original work of Brockenbrough, Braunwald and Morrow (1)). At rest, the LVOT gradient is measured at 80mmHg (a) with a pulse pressure of 60mmHg (b). Following an extrasystolic beat (VPC) there is an increase in both LVOT gradient (A) and pulse pressure (B) to 115mmHg and 90mmHg respectively.

Dynamic LVOT obstruction occurs when the ejection orifice is narrowed by increased force of LV contraction2. This can occur during catecholaminergic stress, exercise, the use of cardiac inotropes and following an extrasystolic beat (post-extrasystolic potentiation). In the latter case, the reduced effective orifice area leads to a fall in stroke volume and the associated fall in aortic pressure.

Even fifty years after its first description, the physiological understanding of dynamic LVOT obstruction is greatly enhanced by the original work of Brockenbrough, Braunwald and Morrow.

The authors have no conflict of interest