43(15) ms in the patients (P < 0 01). Q to the onset of mitral regurgitation was also short (50(15)) ms, and correlated inversely with PR interval (r. = -0-67, n = 73, P < 0*01). Early potentials (< 40 uV) were recorded on the signal averaged electrocardiogram in 33 representative patients and in all controls. Their overall duration was 30(12) ms in the patients, much longer than normal (12(7), P < 0.01)). Early potential time correlated positively with PR interval (r = 0'75, P < 0.01) and QRS duration (r = 0-60, P < 0.01) on a 12 lead electrocardiogram, and negatively with apparent electromechanical delay (r = -071, P < 0.01, n = 33), but not with true electromechanical delay (73 (15) (Br HeartJ7 1994;72:167-174) Prolonged ventricular activation, as shown by a broad QRS complex, is common in patients with dilated cardiomyopathy' 2 and may independently impair systolic and diastolic ventricular function.2' Such patients are often said to have "left bundle branch block", but the body of direct information from humans underlying this diagnosis is surprisingly scanty. The electrocardiographic pattern in these patients is very variable, particularly as to the presence or absence of a septal q wave. Also, the QRS duration is unimodally distributed in a large population of such patients,2 which would be surprising if the long QRS complex were indeed due to the presence or absence of a localised block of a single anatomical structure. In our study, therefore, we have attempted to clarify some of these questions by combining detailed findings of regional ventricular wall motion with information from standard 12 lead and signal averaged electrocardiograms in a group of patients with dilated cardiomyopathy. Patients and methods PATIENTSWe studied 77 patients aged 59(SD13). All the patients had dilated cardiomyopathy, defined as left ventricular end diastolic dimension 6-0 cm or more and shortening fraction < 15% on an M mode echocardiogram. Four

Objective-To compare the different effects of right ventricular pacing and classic left bundle branch block on left ventricular function.Design-Retrospective and prospective study of 48 patients by electrocardiography, and M mode, cross sectional, and Doppler echocardiography.Setting--A tertiary cardiac referral centre.Patients-48 patients (age range 21 to 89 years, 15 women), 24 with a VVI pacemaker implanted and 24 with classic left bundle branch block. Functional mitral regurgitation was present in all those with right ventricular pacing and 22 of those with left bundle branch block.Results-Age, RR interval, and left ventricular size were similar in the two groups, as were conventional measurements of overall systolic function: shortening fraction and pre-ejection and aortic ejection times. In right ventricular pacing, however, QRS duration (p < 0.01) and electromechanical delay were much longer (p < 0.001), whereas the time intervals from onset of mitral regurgitation to aortic opening (contraction time) and from A 2 to the end of mitral regurgitation (relaxation time)were consistently shorter (p < 0.01) than corresponding values in patients with left bundle branch block. Reversed splitting of the second heart sound was much commoner in left bundle branch block (p < 0.02), and only these patients showed an early systolic ventricular septal contraction. Its onset folilowed the initial deflection of the QRS complex by Conclusions-The left ventricle seems to be activated much more rapidly with right ventricular pacing than with left bundle branch block. This applies even when left bundle branch block is present before pacing. Electromechanical delay, contraction and relaxation times, and extent of incoordinate ventricular wall motion differ strikingly between the two conditions. The use of right ventricular pacing as an experimental model of left bundle branch block in humans must be re-examied. (Br Heart J7 1993;69: 166-173) Right ventricular pacing has been used to simulate the mechanical effects of left bundle branch block in experimental models and clinical studies.' 2 Although clearly different in activation pathway and electromechanical delay,34 the mechanical effects of the two modes of activation have not been systematically compared. We have, therefore, investigated the differences and similarities between the two, by a series of non-invasive tests. Patients and methods PATIENTSWe studied 48 patients; 24 of these had a VVI pacemaker implanted (with the electrode tip in the right ventricular apex) for complete heart block and 24 had normal atrioventricular conduction but classic left bundle branch block. The diagnostic criteria of left bundle branch block included QRS duration 166

plotted against the direct record. The plots confirmed that the reconstructed pressure was always less than directly measured pressure, the relative degree of underestimation falling as the pressure rose. This was not the effect of acceleration, but probably reflects changing geometry of the regurgitant orifice. Conclusion-The continuous wave Doppler trace of functional mitral regurgitation is suitable for studying the timing of overall mechanical events and normalised rates of change of pressure in the left ventricle. Estimates of atrioventricular pressure drop by this method and particularly its absolute rates of change seem to be less reliable. (Br HeartJ 1995;73:53-60) Keywords: mitral regurgitation, Doppler measurement.The time course of left ventricular pressure has long been used to assess left ventricular mechanical activity. In 1921, Wiggers described the phases of a cardiac cycle using the combination of left ventricular and aortic pressure pulses,' and noted that the time course of left ventricular pressure could be affected by activation pattern.23 More recently, the ventricular pressure pulse has been used to time the onset and duration of mechanical systole45 and to assess an entity described as "contractility" from its peak rate of change.

Funding Acknowledgements Type of funding sources: None. Introduction Aortic dilatation is most commonly associated with hypertension, bicuspid aortic valve and connective tissue diseases such as Marfan’s. It is a precursor to life threatening complications such as rupture or dissection of the aorta. The current ESC Guidelines recommend surgical intervention once the aortic diameter is &gt;50 mm in patients with Marfan syndrome (Ic) and &gt;55 mm in patients with a bicuspid or normal aortic valve morphology (IIb). There is currently a lack of literature on the prevalence of aortic dilatation in the general or even hospital population although there is historical data suggesting the incidence of thoracic aortic aneurysm to be 5.9 cases per 100,000. Purpose The aim is to investigate the prevalence of aortic dilatation by echocardiography in our hospital population which may help lay the foundation for population studies and identify prognostic factors which may determine the time of surgical intervention. Methods We carried out a retrospective survey using the digital echocardiogram archive and the electronic patient record system at our hospital. This survey covered the period between 1st October 2016 and 1st November 2018. For randomisation  purposes, all transthoracic echocardiograms (TTE) performed on every Thursday during this period were included. All patients with an echocardiographic report of aortic root or ascending aorta dilatation were enrolled. Other information including echocardiographic dimensions along with demographics and past medical history was collected. Results During this 24-month period, we analysed a total of 3019 TTEs. 209 patients (6.9%) were reported to have aortic dilatation. 137 (66%) were male and the median age was 67 years. The mean height and weight were 169cm and 80kg, respectively.  A bicuspid aortic valve was confirmed in 10 (4.8%) patients. 132 (63%) patients had a history of hypertension. On echocardiogram, 75 (36%) patients had septal hypertrophy and 26 (12.4%) had a dilated left ventricle.   Conclusion Our findings are unique and for the first time, to our knowledge, we report the echocardiographic prevalence of aortic dilatation in the hospital population (6.9%). It is a staggering 40-fold increase when compared to the the prevalence of aortic aneurysm, the most likely end point of aortic dilatation. Based on our figures, there would be at least 400 patients with a dilated aorta in a year in our hospital alone. The prevalence of bicuspid aortic valve in our cohort (4.8%) was nearly three times higher than the general population where it is quoted as 1-2%. Our study also emphasised the established link between hypertension and aortic dilatation with an increased frequency in our cohort (63%) compared to the global prevalence (31%). Given the devastating sequelae of aortic dilatation and its increased prevalence in our patient population, it will be very important to keep these patients under routine surveillance and particularly those with hypertension.

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