Since the work of Wolferth and Margolies (1935), the modifications of both the heart sounds and the sequence of ventricular events induced by left bundle-branch block have been well known. Yet there has been some disagreement on details, mainly because left bundle-branch block is seldom aft isolated abnormality. The opportunity was offered to record the heart sounds, the indirect carotid pulse, and the apex cardiogram in the same patient, in conditions of both normal and abnormal left intraventricular conduction, making it possible to describe the changes due to the complete bundlebranch block alone. METHODThe electrocardiogram, phonocardiogram, indirect carotid pulse curve, and the apex cardiogram were recorded with a photographic 4-channel Hellige Multicardiotest. The phonocardiogram, dissociated into three frequency bands, low, medium, and high, ranging respectively from 5 to 50, 25 to 150, and 50 to 250 cycles per second, was taken successively from three areas, apical, pulmonary, and aortic, simultaneously with the electrocardiographic lead I. Next, these same phonocardiograms (low and high frequencies only) and electrocardiographic lead I were recorded either with an indirect carotid pulse curve (capacitance transducer Infraton-E system) or with an apex cardiogram (piezoelectric crystal transducer). Paper speed was 50 mm. per second with 0-02 sec. intervals between the vertical lines.The following time intervals were measured after Tafur, Cohen, and Levine, 1964 (Fig. 1). (1) Electromechanical interval (EMI) from the onset Received July 11, 1966. 520 ofthe QRS complex of the electrocardiogram to the onset of the systolic wave of the apex cardiogram (ACG).(2) First pre-ejection component of ventricular con. traction (PEC-I) from the onset of the systolic wave of the ACG to the notch on its ascending limb which marks mitral valve closure (MC), and corresponds normally to the first rapid vibrations of the 1st heart sound.(3) Second pre-ejection component of ventrticular contraction (PEC-II) from MC on the ascending limb of the ACG to the onset of the indirect carotid pulse (OCP). In the present study, this interval was not measured but calculated by subtraction of the average QRS to MC interval from the average QRS to OCP interval (Q-OCP).(4) Ejection phase of ventricular contraction from the OCP to its dicrotic notch, which marks aortic valve closure.(5) Isometric relaxation phase from the aortic component of the 2nd sound (A2) on the phonocardiogram to the lower-most point " 0 " of the ACG, which marks mitral valve opening.(6) Ventricular filling phase from the point "0" to the onset of the following systolic wave of the ACG.

The electrocardiographic signs of left complete bundle-branch block are now well established, and in the majority of cases they correspond to total or subtotal destruction of the left bundle-branch fibres (Lenegre, 1957). However, two sorts of problems remain under discussion, namely, demonstration of the left ventricular delay in atypical cases of left bundle-branch block, for example when left bundlebranch block masquerades as right bundle-branch block (Richman and Wolff, 1954), and demonstration of the type of disturbed left intraventricular conduction, whether bundle-branch or arborization block, in typical cases with abnormal QRS prolongation (Grant and Dodge, 1956).In a previous paper one case of intermittent left complete bundle-branch block was reported, which offered the opportunity to recall the signs of left ventricular delay, derived from the phonocardiogram and mechanocardiogram, i.e. indirect carotid pulse curve and apex cardiogram (Baragan et al., 1967). The purpose of the present study was to analyse the heart sounds and the mechanocardiographic curves of a relatively large number of chronic cases of left complete bundle-branch block, with the hope that they may help to answer, in the future, the two sorts of problems mentioned above. PATIENTS AND METHODThe group consisted of 30 clinical cases of miscellaneous heart diseases, the electrocardiograms of which met the classical criteria for left complete bundle-branch block, namely, a QRS complex of supraventricular origin or more in lead V6. There were 20 men and 10 women with an average age of 48-5 years (range 18 to 78). The aetiological factors responsible for the heart condition associated with the pattern of left complete bundlebranch block were valvular heart disease (10 cases), ischaemic heart disease (6 cases), primary non-obstructive cardiomyopathy (6 cases), obstructive cardiomyopathy (3 cases), systemic hypertension (3 cases), and idiopathic left complete bundle-branch block (2 cases). Of these, 2 cases of left complete bundle-branch block resulted from operation, and one case, which had already a left complete bundle-branch block before operation, was aggravated by the latter. Of the 30 cases, 18 were in, or had just recovered from, cardiac failure.The electrocardiogram, phonocardiogram, indirect carotid pulse curve, and the apex cardiogram were recorded with a photographic 4-channel Hellige Multicardiotest. The phonocardiogram, dissociated into two frequency bands (low from 5 to 50, and high from 50 to 250 cycles per second), was recorded simultaneously with an electrocardiographic lead, and alternatively either with an indirect carotid pulse curve (capacitance transducer Infraton-E system) or with an apex cardiogram (piezo-electric crystal), the patient lying in the left lateral position. Records were taken at a paper speed of 50 mm. per second, with the vertical lines separated by intervals of 0-02 second.The following time intervals were measured ( Fig. 1

The time intervals defined by the simultaneous recording of an electrocardiogram, phonocardiogram, indirect carotid pulse curve, and apexcardiogram made it possible to compare the left ventricular (LV) dynamics in a group of 33 cases of complete right bundle-branch block with left axis deviation (RBBB-LAD) with two control groups, one consisting of 30 cases of complete right bundle-branch block without left axis deviation (RBBB without LAD) and the other of 30 cases of left axis deviation (LAD) alone.The LV dynamics of RBBB-LAD differed from those of both control groups of RBBB without LAD and of LAD alone by a significantly late onset of LV ejection in the former, resulting from both late onset and slow rise of LV contraction. On the other hand, the delayed LV activity was not significantly different between the group of RBBB-LAD and a previously studied group of complete left bundle-branch block.Normal limits for these intervals were looked for to make it possible to diagnose a late LV activity in the individual patient, and so provide a further argument in the discussion for an eventual cardiac pacing in doubtful cases.Finally, it was not felt possible to use these intervals to try to localize the site of the conduction disturbance, whether in the bundle branch or in the ventricular wall itself.

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