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Biomedical subjects

J C Mohan

Publications and source records attributed to J C Mohan.

At least 91 records · Page 5Linked to original sources
PubMedDate not supplied

Acute hemodynamic effects of different atrioventricular intervals in dual chamber pacemakers: is there an optimum atrioventricular delay.

Conflicting data have been reported regarding adjustment of atrioventricular (AV) interval to maximise hemodynamic performance of dual chamber pacemakers. Eleven consecutive patients with complete heart block and dual chamber pacemakers were paced at three AV intervals (150, 200, 250 msec) and free running rates (60-93 bpm, mean 73 +/- 12 bpm) with simultaneous measurements of cardiac output, atrial contribution to left ventricular filling, left ventricular ejection fraction, and peak aortic velocity and acceleration by echo-Doppler techniques to define the optimum AV delay. At all the three AV intervals tested there was no difference in cardiac output (4.7 +/- 0.96, 4.83 +/- 1.12, 4.77 +/- 1.19 litres/min respectively, p = NS), left ventricular ejection fraction (60.2 +/- 10.6%, 61.2 +/- 9.9% and 64 +/- 8.3%, p = NS), atrial contribution to left ventricular filling (0.37 +/- 0.10, 0.38 +/- 0.09, 0.36 +/- 0.16, n = 8, p = NS), peak aortic velocity (104 +/- 8, 105 +/- 12, 104 +/- 13 cm/sec, p = NS) and aortic acceleration (19.68 +/- 4.26, 20.4 +/- 5.58 and 19.0 +/- 4.54 m/sec2, p = NS). Compared to AV delay of 150 msec an increase in cardiac output of 0.5 L/minute was observed in three patients at an AV delay of 200 msec and in one patient at the AV delay of 250 msec. These data suggest that it is difficult to generalize an optimum AV delay in patients with dual chamber pacemakers. With the AV interval in the range of 150-250 msec, only a minority of patients could improve their haemodynamics at rest by adjusting this interval if the baseline cardiac function was normal.

Adult↗
PubMedDate not supplied

Experience with recycled cardiac pacemakers.

Twelve years experience with pacemaker re-use is reported. Between November 1979 and December 1991, forty two pacemakers were re-used in 42 patients after in-hospital reconditioning. There were 31 males and 11 females in the age range of 29 to 84 years (mean 59 +/- 13 years). In 29 patients, the pulse generator was explanted because of pocket infection and/or impending extrusion, and it was re-implanted at a new site after sterilization. In the remaining 13 patients pacemakers explanted from other patients were implanted because of economic reasons. All patients were regularly followed up in the pacemaker clinic for a mean duration of 34 +/- 35 months (range 6-126 months). There was one infection and one erosion after 12 and 27 months respectively. One of these units was resterilized and implanted without any recurrence of infection or erosion over a follow up of 12 months. There was no adverse reaction or pulse generator failure. Our experience suggests that the use of refurbished pacemakers is a safe and economically viable option.

Adult↗
PubMedDate not supplied

Long term performance of silicone insulated and polyurethane insulated cardiac pacing leads.

The long term performance of various pacing leads in use for at least one year is reported from one centre. Between January 1975 and December 1990, 1056 cardiac pacing leads were implanted in 881 patients (mean age 57 +/- 13 years). Eight hundred and three leads were silicone insulated (SI) and 253 leads were polyurethane insulated (PUI). Leads from different manufacturers were used (Medtronic, CPI, Telectronics). The average duration of follow up was 56.6 +/- 77 months (range 12-221 months) for SI and 47.1 +/- 24 months (range 12-99 months) for PUI leads. Overall lead failure occurred more often in the PUI group (n = 46, 18.2%) compared to SI group (n = 93, 11.3%, p < 0.025). Majority of lead failures occurred in the first 36 months after implantation. In particular, Medtronic models 6971, 6972 (urethane) and 6901 (silicone) showed higher rate of complications (25.5%, 26.3% and 44.5% respectively).

Adolescent↗
PubMedDate not supplied

Colour Doppler echocardiographic quantification of prosthetic aortic valve regurgitation in patients with normally functioning Bjork-Shiley prostheses.

Colour Doppler echocardiographic studies were performed in 46 patients (age range 16-35 years, mean 26 +/- 8; male 31, female 15) with normally functioning Bjork-Shiley prostheses in aortic position to estimate transprosthetic regurgitation. Regurgitant jet length and height were measured and assessed in multiple views. All patients showed prosthetic regurgitation of varying degree. Regurgitant jets were central in all but 3 (6.5%) patients. Single jets were seen in 28 (61%) and double jets in 18 (39%). Jet height in parasternal long axis view ranged from 0.4 to 1.2 cm (mean 0.7 +/- 0.4 cm) and jet height to left ventricular outflow tract diameter ratio was 0.22 to 0.48 (mean 0.38 +/- 0.13). Prosthetic regurgitation was < or = 2/4 grades in 42 (91%) patients, and combined height of double jets (n = 18) was less than that of the single jets (n = 28) (0.5 +/- 0.3 cm vs 0.8 +/- 0.4 cm, p < 0.05). In conclusion, colour Doppler examination frequently detects prosthetic regurgitation in patients with aortic Bjork-Shiley prostheses; regurgitation is grade 2/4 or less in most of the patients, is overestimated in patients with a single jet and weakly correlates with prosthesis size.

Adolescent↗
PubMedDate not supplied

M-shaped doppler signal across ventricular septal defect: potential implications for estimation of right ventricuilar systolic pressure.

An 8-year-old child suffering from ventricular septal defect and severe valvular pulmonary stenosis was evaluated by echo-Doppler technique and cardiac catheterization. A peak instantaneous transventricular systolic gradient of 64 mmHg was recorded across the ventricular septal defect with an interesting M-shaped spectral pattern. However, cardiac catheterization revealed a peak-to-peak non-simultaneous gradient between the right and the left ventricle of only 14 mmHg. This discrepancy along with its implications are discussed in this report.

Cardiac Catheterization↗
PubMedDate not supplied

Effect of preload and heart rate manipulation on Doppler transmitral flow velocity pattern: search for load--independent parameters.

Pulsed Doppler transmitral flow-velocity provides a non-invasive method for serial evaluation of diastolic function. However confounding influence of loading conditions and heart rate on transmitral flow makes many conclusions suspect. To study the effect of preload, various parameters of Doppler mitral spectrum were studied in 11 patients with stable effort angina, angiographic coronary artery disease and intact global and segmental systolic function, before and after administration of sublingual isosorbide dinitrate (group 1). Following isosorbide dinitrate administration, there was a significant increase in heart rate (p less than 0.001), decrease in left ventricular end-diastolic volume (p less than 0.01), no change in left ventricular ejection fraction and systolic blood pressure. Peak E velocity, E velocity-time integral, E/A velocity time integrals ratio, acceleration and deceleration rates and diastolic filling period were significantly reduced whereas peak A velocity, A velocity time integral, acceleration and deceleration times and atrial filling period were unchanged. In 10 age-matched patients (group 2), atrial pacing performed to achieve similar degree of increase in heart rate as in group 1 (10 +/- 1 vs 12. +/- 4, p = NS), resulted in a decrease in E velocity time integral, E/A velocity time integrals ratio and diastolic filling period (p less than 0.01) without any significant change in any other parameter. Absolute A velocity time integral, acceleration and deceleration times are the only parameters of transmitral diastolic flow-velocity profile which are relatively independent of preload and heart rate provided the change is small.

Administration, Sublingual↗
PubMedDate not supplied

Electrocardiographic features of atrial depolarization during pacing of right atrial appendage.

Identification of atrial capture during pacing from right atrial appendage is frequently difficult. Electrocardiograms of forty five patients implanted with AAI/DDD pacemakers (thirty unipolar, fifteen bipolar) were analysed to characterize the specific morphology of paced P waves. Compared to sinus P waves, atrial pacing resulted in atrial depolarization of lower amplitude (0.16 +/- 0.05 mv vs 0.11 +/- 0.032 mv, P less than 0.005) but increased duration (0.07 +/- 0.009 sec vs 0.08 +/- 0.017 sec, P less than 0.005). P wave morphology was similar in unipolar and bipolar pacing units. It was positive in lead I (80%), II (71.11%), III (80%) and aVF (75.55%). In lead aVL, paced P waves were usually diphasic with an initial negative deflection (35.55%). Precordial leads showed paced atrial depolarization of small amplitude and did not help in identification of atrial capture. In unipolar pacing P waves were best seen in lead III because of small pacing spike in this lead. Lead II was suitable for identification of paced P waves in bipolar pacing. Thus careful examination of standard ECG leads for paced P waves of low amplitude, prolonged duration and specific morphology can help in confirming atrial capture following pacing stimulus from right atrial appendage.

Adult↗
PubMedDate not supplied

Clinical utility of transoesophageal echocardiography--preliminary experience of 100 cases.

We performed transoesophageal echocardiography (TEE) and compared its results with transthoracic echocardiographic (TTE) studies in a consecutive series of 100 cases. TEE was performed with a 5 MHz transducer with pulsed wave, continuous wave and colour Doppler facilities. All the patients were in unsedated state; the initial 50 were, in addition, monitored noninvasively for any change in heart rate, blood pressure or arterial oxygen saturation. The procedure was well tolerated by all; one patient had transient ventricular bigeminy. Except increase in heart rate and systolic blood pressure at the time of insertion of probe, there was no change in any of the clinical parameters studied. In patients of mitral stenosis, a thrombus in left atrium (LA) or left atrial appendage (LAA) was seen in 7/52 TEE studies, as compared to 4/52 TTE studies. LAA thrombi (2 cases) were detected only on TEE. Following balloon mitral valvuloplasty, a small atrial septal defect was seen in 6/8 TEE, but only 2/8 TTE studies. In 20 cases with doubtful atrial septal defects on TTE, TEE revealed an intact septum in 6 and delineated the anatomy of the defect in the remaining 14. TEE facilitated detection and better visualisation of paravalvular regurgitation in 4 cases with mitral and 3 cases with aortic valve prosthesis. In addition, TEE helped in excluding vegetations in 3 suspected cases of infective endocarditis and in studying details of 2 intracardiac masses. We conclude, TEE can be safely performed in conscious unsedated patients and provides valuable information in addition to transthoracic echocardiography.

Adult↗
PubMedDate not supplied

Double outlet right ventricle with calcified rheumatic mitral stenosis.

A 21-year old female patient diagnosed to have double outlet right ventricle, ventricular septal defect, pulmonic stenosis and right-to-left shunt on cardiac catheterisation in childhood, presented with a recent onset right sided hemiparesis and congestive heart failure. Investigative data revealed atrial fibrillation, severe calcific mitral stenosis and multiple left atrial thrombi in addition to the previously reported findings. The diagnosis was confirmed by cross-sectional and colour Doppler echocardiography.

Adult↗
PubMedDate not supplied

Verapamil responsive ventricular tachycardia: clinical and electrophysiologic characteristics.

Ventricular tachycardia is a rare arrhythmia in young patients without associated heart disease. Electrophysiologic studies were performed in thirteen young patients (mean age 26.4 +/- 7 years) with recurrent sustained ventricular tachycardia (VT) responsive to intravenous verapamil. The QRS duration during VT was less than 0.14 sec in all patients. The VT showed a right bundle branch block (RBBB) morphology in all cases, with left axis deviation in 12 and right axis deviation in one. Eleven patients were free of organic heart disease. VT could be induced in the laboratory in 10 patients, out of whom the electrophysiologic mechanism of VT could be assessed in 9 cases. The data were consistent with reentry in 8 patients and suggested triggered activity in one patient. Atrial pacing induced the VT in two cases. Nine patients were restudied 48 to 72 hours after oral verapamil (240 to 320 mg/day). VT was not inducible in 8 patients and was markedly slowed in one. VT of RBBB morphology occurring in young patients has distinct electrocardiographic and electropharmacologic properties. Reentry is the usual underlying mechanism. Verapamil is highly effective in terminating and preventing the VT.

Adolescent↗
PubMedDate not supplied

Electrophysiologic effects of oral propafenone in Wolff-Parkinson-White syndrome studied by programmed electrical stimulation.

We studied the electrophysiologic effects of oral propafenone on induction of supraventricular tachycardia (SVT) in 10 patients with Wolff-Parkinson-White syndrome (5 manifest and 5 concealed accessory pathways). Nine patients had orthodromic SVT and one patient had atrial fibrillation with preexcited QRS (shortest RR 220 msec). Electrophysiologic studies were performed during control and 48 hours after oral propafenone administered in a dose of 300 mg every eight hours. Propafenone caused complete anterograde accessory pathway conduction block in 4 of 5 patients with manifest delta waves. Retrograde conduction through the accessory pathway was abolished in 6 of 9 patients in whom it was present during control. Sustained SVT was inducible in all 9 patients during control. Propafenone prevented induction of SVT in 8 of 9 patients (88.9%) and slowed the rate of induced SVT in one patient. In the patient with atrial fibrillation (AF) the accessory pathway was blocked and AF was not inducible. There was a significant increase in the effective refractory period (ERP) of the atrium (208 +/- 40 msec to 257 +/- 25 msec, p less than 0.01), atrioventricular (AV) node (less than or equal to 256 +/- 34 msec to greater than or equal to 324 +/- 35 msec, p less than 0.001) and ventricle (204 +/- 14 msec to 262 +/- 51 msec, p less than 0.01). The atrial paced cycle length at AV nodal block also increased from 288 +/- 51 msec to 389 +/- 51 msec (p less than 0.01) after the drug. Thus propafenone has potent inhibitory effects on accessory pathways and has additional significant effects on atrial, AV nodal and ventricular refractoriness.

Administration, Oral↗
PubMedDate not supplied

Non-surgical mitral valvuloplasty for rheumatic mitral stenosis.

One hundred and twenty-six patients of rheumatic mitral stenosis (MS), aged 10-30 (mean 19.5 +/- 5.9) years underwent balloon mitral valvuloplasty (BMV). All valvuloplasties were done by the anterograde transvenous, transatrial route. The procedure was successful in 120 (95%) cases. Single balloon was used in 10 patients early in the series and double balloon was used in the other 110 patients. BMV resulted in a significant increase in the mitral valve area (MVA) from 0.96 +/- 0.35 to 2.3 +/- 0.8 cm2 (p less than 0.0001) and a significant fall in the transmitral pressure gradient (TMG) from 28.2 +/- 3.2 to 7.4 +/- 4.8 mmHg (p less than 0.001). The MVA achieved by BMV was found to have a significant positive correlation with the balloon diameter to body surface area ratio (BD/BSA) (r = 0.69, p less than 0.001). New mitral regurgitation (MR) developed in 15 patients--trivial in 11, 2+ in 2 and 3+ in 2. One patient required emergency mitral valve replacement. Procedure induced MR did not have a significant relation to the balloon size, degree of mitral sub-valvular pathology or the severity of mitral stenosis. Iatrogenic atrial septal defect was detected by oximetry in none, by angiography in one patient, and by Doppler color flow imaging in 5 patients. Cardiac tamponade was the most frequent serious complication, occurring in 6 patients, 4 of whom died following emergency surgery. Sixty-five patients have been followed up for at least 6 months (range 6-30, mean 16.3 +/- 6.3 months) following BMV.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMedDate not supplied

Short term hypolipidemic effects of oral lactobacillus sporogenes therapy in patients with primary dyslipidemias.

Short term hypolipidemic effects of oral Lactobacillus sporogenes (360 million spores/day) were studied in 17 patients (mean age 45.6 years; males 15, females 2) with type II hyperlipidemia in an open label fixed dose trial. Over a period of 3 months, significant reductions were observed in total cholesterol (330 +/- 55 mg% to 226 +/- 46 mg%, p less than 0.001) and LDL-cholesterol (267 +/- 58 mg% to 173 +/- 54 mg%, p less than 0.001). The HDL-cholesterol was marginally increased (43.6 +/- 7 mg% to 46.8 +/- 8.9 mg%, p less than 0.05). There was no change in serum triglyceride concentration. Total cholesterol/HDL cholesterol and LDL cholesterol/HDL cholesterol ratios were significantly reduced after treatment (p less than 0.001). No adverse effect was noted. While the change in serum lipid levels on treatment was consistent with regard to total and LDL-cholesterol, it was not so in case of serum triglycerides and HDL-cholesterol. Oral Lactobacillus sporogenes therapy may prove to be an important hypolipidemic therapy after confirmation in larger trials.

Adult↗
PubMedDate not supplied

Comparison of atrial and VVI pacing modes in symptomatic sinus node dysfunction without associated tachyarrhythmias.

The natural course of patients with symptomatic sinus node dysfunction who did not have associated tachyarrhythmias before pacemaker implantation was compared after VVI and atrial pacemaker implantation. Between April 1981 and June 1989, forty-seven such patients (mean age 52 + 13 years) received VVI pacemakers and forty patients (mean age 54 + 13 years) received AAI or DDD pacemakers. Baseline clinical characteristics and severity of sinus node dysfunction were comparable in the two groups. Over a follow up of 10 to 96 months (mean 49.2 + 26 months), 11 (23.4%) VVI patients were in functional class II or more compared to 2 (5%) atrially paced patients (p less than 0.01). Other complication rates were also higher in the VVI group as compared to AAI group viz. atrial fibrillation (21.2% vs 2.5% p less than 0.01) and stroke (10.6% vs 2.5%) though the number of deaths (14.9% vs 10%) was not significantly different in the two groups. Two patients in atrial paced group and one patient in VVI group developed first degree heart block. There was no incidence of second or third degree heart block. Transient loss of atrial sensing occurred in 3 patients and atrial lead displacement in 2 cases, but overall incidence of lead related problems was low and comparable in both groups. Thus atrial pacing is superior to ventricular pacing in sinus node dysfunction and risk of developing high grade atrioventricular block on follow up is low.

Adult↗
PubMedDate not supplied

Determinants of left ventricular function in isolated rheumatic mitral stenosis.

Left ventricular end-diastolic volume (preload), peak systolic wall stress (afterload), instant Emax (contractility index = peak systolic left ventricular pressure/end-systolic volume), left ventricular mass, left ventricular ejection fraction (LVEF) alone and normalised for mass index, were studied in 30 patients with isolated rheumatic mitral stenosis (group 1) and compared with 24 normal individuals (group II) who served as control. Preload was not different in the two groups (p = NS), afterload was increased in group I (p = 0.01), while LVEF, Emax, left ventricular mass and mass normalised LVEF were reduced in mitral stenosis as compared to normal control (p less than 0.01- less than 0.001). Comparison of patients with reduced ejection performance (LVEF less than 50%, n = 9, group IA) with those having normal LVEF (n = 21 group IB) revealed increased left ventricular end-diastolic volume and reduced left ventricular mass, mass normalised ejection fraction and Emax (in IA p less than 0.05). Peak systolic wall stress was comparable in these two subgroups. This study shows that the major determinant of left ventricular dysfunction in isolated rheumatic mitral stenosis is impaired contractility and not the loading factors.

Adolescent↗