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Biomedical subjects

A S Sundar

Publications and source records attributed to A S Sundar.

15 recordsLinked to original sources
PubMed1996

Impaired matching of perfusion and ventilation in heart failure detected by 133xenon.

In severe chronic heart failure (CHF) the ventilatory cost of CO2 elimination during exercise (VE/VCO2) is increased, suggesting ventilation/perfusion (V/Q) mismatch. The relationship of exercise VE/VCO2 regression slope m to deadspace ventilation was studied in 15 patients with CHF who underwent cardiopulmonary exercise testing and arterial blood gas monitoring. Regional lung ventilation and perfusion was studied, using 133xenon, at rest and peak exercise in a further group of 10 CHF patients and in five normal subjects. VE/VCO2 slope m correlated well with deadspace ventilation at peak exercise in the 15 patients with CHF. We therefore used exercise VE/VCO2 slope m to categorize CHF patients undergoing 133xenon imaging into groups with increased (slope m > 36) or normal (slope m < 36) exercise deadspace ventilation. In normals, resting V/Q determined by 133xenon showed a gravitational gradient, which improved on exercise as a result of relative increases and of relative reductions in regional perfusion; no significant changes in regional ventilation distribution were detected. In patients with CHF who had normal slope m (n = 5), rest and exercise V/Q were similar to the normal subjects. In CHF patients with increased slope m (n = 5) however, the resting gravitational gradient of V/Q was lost, and there were no significant changes in relative perfusion distribution on exercise. These findings suggest that the increased ventilatory cost of CO2 elimination found in certain patients with CHF is related to inability to coordinate and optimise the relative distribution of lung perfusion with respect to ventilation during exercise.

Adult↗
PubMed1992

Anomalous origin of the right coronary artery from the pulmonary artery in association with congenital aneurysm of the sinus of Valsalva: angiographic diagnosis of a rare association.

A 37 year old man presenting with acute heart failure, hypotension, and acute renal failure was diagnosed by cardiac catheterisation and angiography to have the rare combination of congenital aneurysm of the non-coronary sinus of Valsalva rupturing into the right ventricle, and an anomalous origin of the right coronary artery from the main pulmonary artery. The diagnosis could not be confirmed by transthoracic echocardiography in this patient. This combination of defects, confirmed at cardiac surgery, has not been reported before, and this case report highlights the importance of preoperative definition of congenital defects associated with an aneurysm of the sinus of Valsalva.

Acute Kidney Injury↗
PubMed1989

Echocardiographic diagnosis of a left atrial thrombus in a patient with normal prosthetic mitral valve.

A 20-year-old male with a Björk-Shiley mitral valve prosthesis on optimal anticoagulation and antiplatelet drug therapy presented with systemic embolization 11 months after mitral valve replacement. Cross-sectional and Doppler echocardiography revealed a left atrial thrombus attached to the posterior wall of the left atrium and normal function of the prosthetic valve. The findings were confirmed at surgery.

Adult↗
PubMed1989

Fixed subaortic stenosis with congenital aneurysm of sinus of Valsalva--cross-sectional and Doppler echocardiographic diagnosis of a rare association.

A 13-year-old girl was diagnosed by cross-sectional and Doppler echocardiography to have the rare combination of congenital aneurysm of the right sinus of Valsalva rupturing into the right ventricular outflow tract and a discrete subaortic fibrous shelf with severe subvalvar stenosis, moderate aortic regurgitation and left ventricular dysfunction. The findings were confirmed at cardiac catheterisation and surgery.

Adolescent↗
PubMed1989

Experience with activity sensing rate responsive ventricular pacing. A study based upon assessment of exercise tolerance.

Fourteen patients (mean age 41 years) who received rate responsive activity sensing VVI pacemakers were studied to evaluate the relationship between the rate response and exercise tolerance by analysing the symptom limited maximum treadmill time both during fixed rate VVI oacubg abd dyrubg VVI + activity mode pacing (RRP). The proper functioning of RRP mode was confirmed by Holter monitoring in all. The indications for pacing were, sino-atrial block with high grade AV block, tachybrady syndrome, atrial fibrillation with complete heart block, congenital complete heart block and persistent slow junctional rhythm. Basic rate was programmed to 70 PPM in both pacing modes; rate response and activity threshold were programmed to 5 and medium respectively. The order in which two pacing modes were tested was chosen randomly. The maximum treadmill time (MTT) was 25.4% longer in the RRP than in VVI mode with a mean of 11.4 minutes in RRP and 8.5 mins in VVI(p less than 0.01). for the subgroup of patients who demonstrated paced only rhythm the average increase in MTT was 31.4% with a mean of 11.8 minutes in RRP and 8.1 mins in VVI (p less than 0.01). Five patients who showed intermittent spontaneous rhythm, increased their average MTT by 22.3% with a mean of 11.2 minutes in RRP and 8.7 mins in VVI mode (p less than 0.05). During RRP a significance positive correlationship was seen between MTT and the increase in heart rate (N = 14, r = 0.85, p less than 0.001).(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMed1987

Percutaneous transluminal balloon pulmonary valvoplasty--long-term results.

Thirty-two patients with isolated valvar pulmonary stenosis (21 male; 11 female, age range 4 to 53 years, mean 14 years) underwent cardiac catheterization and balloon valvoplasty. Right ventricular systolic pressure before valvoplasty ranged from 65 to 210 mm Hg (mean 120.2 +/- 44.8 mm Hg). It fell to 24-200 mm Hg (mean 73.1 +/- 42.4 mm Hg) immediately after dilation. Peak systolic gradient across the pulmonary valve before valvoplasty ranged from 42 to 193 mm Hg (mean 98 +/- 45.3 mm Hg) and decreased significantly to 5 to 182 mm Hg (mean 52.7 +/- 43.1 mm Hg) immediately after dilation. At repeat cardiac catheterization in 21 patients 3 to 6 months after valvoplasty, a further significant fall of gradient was noted in 15 patients with no change in the remaining six patients. The right ventricular systolic pressure ranged from 30 to 100 mm Hg (mean 55.1 +/- 21.8 mm Hg) while the transpulmonary gradient varied from 12 to 84 mm Hg (mean 34 +/- 23.8 mm Hg). In the four patients evaluated 1 to 1 1/2 years after valvoplasty, the gradient further reduced in 2 patients and was unchanged in the remaining two patients. Patients with isolated valvar pulmonary stenosis can be adequately and safely treated with balloon valvoplasty, without recourse to surgery with excellent immediate and long-term results.

Adolescent↗
PubMed1987

Quantitative assessment of pulmonary hypertension in patients with rheumatic heart disease using continuous wave Doppler ultrasound.

The accuracy of Doppler ultrasound in estimating pulmonary arterial systolic pressure non-invasively was evaluated in 50 patients with rheumatic heart disease. In all cases, the maximal velocity of the tricuspid regurgitation jet was measured by continuous wave Doppler ultrasound and the systolic pressure gradient between right ventricle and the right atrium was calculated by the modified Bernoulli equation. There was a close correlation between Doppler estimated and hemodynamically measured transtricuspid systolic gradient (r = 0.86, P less than 0.001). Right ventricular systolic pressure, which equals pulmonary arterial systolic pressure in the absence of right ventricular outflow obstruction, was calculated by adding a constant of 10 to the Doppler gradient and also by using a regression equation. Right ventricular systolic pressure obtained by both of these Doppler methods correlated closely with values at cardiac catheterization (r = 0.82 and 0.83, respectively). Our study suggests that pulmonary arterial systolic pressure can be determined non-invasively with accuracy, by Doppler ultrasound, in patients with rheumatic heart disease.

Adolescent↗
PubMed1987

Continuous wave Doppler assessment of patients subjected to pulmonary balloon valvoplasty.

To evaluate the role of Doppler ultrasound in accurately quantitating patients with valvar pulmonary stenosis, we studied 30 patients (20 patients undergoing balloon pulmonary valvoplasty before and after the procedure, and 10 patients who had previously undergone pulmonary balloon valvoplasty) by Doppler echocardiography and cardiac catheterization. The peak systolic gradient was calculated by the two methods within 24 hours of each other. The maximal velocity of blood flow was obtained by non-imaging, continuous wave Doppler ultrasound examination performed from various parasternal and subcostal positions and the valve gradient was calculated using a modified Bernoulli's equation. Transpulmonary peak systolic gradient calculated by Doppler examination ranged from 9 to 159 mm Hg (mean 54.8 +/- 34.5 mm Hg) and correlated well with values obtained at cardiac catheterization (r = 0.94, P less than 0.001). Thus our study shows that accurate quantification of pulmonary valve stenosis can be reliably undertaken non-invasively utilizing Doppler echocardiography.

Adolescent↗
PubMedDate not supplied

Echocardiographic assessment of the size of aortic and pulmonary valve annulus before balloon valvoplasty.

Two dimensional echocardiographic measurements of the size of aortic and pulmonary valve annulus were made in 60 patients before balloon valvoplasty and compared to the angiographic measurements. Aortic valve annulus was measured in 34 patients (26 with valvar aortic stenosis and 8 with discrete subaortic stenosis) in the parasternal long axis or apical 5-chamber views. The pulmonary valve annulus was measured in 26 patients with valvar pulmonary stenosis (PS) in the parasternal short axis view of the right ventricular outflow view. The visualization of the annulus was good in all except 2 patients with valvar PS. Angiographic measurements of the aortic and pulmonary valve annulus were made in aortic root and right ventricular angiograms respectively, taken in both right and left anterior oblique views. There was an excellent correlation between the measurements of the annulus size by the two techniques (r value for pulmonary valve 0.91; for aortic valve 0.96; over all 0.94). Echocardiography can accurately measure valve annulus size and help in choosing balloon dilatation catheter of appropriate size before the valvoplasty procedure.

Adolescent↗
PubMedDate not supplied

Long-term efficacy of balloon pulmonary valvoplasty in late adult life.

We performed percutaneous transluminal balloon valvoplasty in a 53-year-old woman with severe valvar pulmonary stenosis. Peak systolic gradient across the pulmonary valve reduced from 112 mm Hg before valvoplasty to 47 mm Hg immediately after dilatation, which further fell to 30 mm Hg six months after valvoplasty with virtual disappearance of gradient at one year follow up. Patients of isolated valvar pulmonary stenosis presenting in late adult life can be adequately and safely treated with balloon valvoplasty, without recourse to surgery with excellent immediate and long-term results.

Catheterization↗