Francis Y.K. Lau

Percutaneous double balloon valvotomy for severe rheumatic mitral stenosis

Percutaneous double balloon valvotomy for severe rheumatic mitral stenosis was successfully performed in 281 of 285 consecutive patients. The changes evoked were a decrease of the mean transvalvular gradient from 16 +/- 7 to 5 +/- 3 mm Hg, an increase in cardiac output from 3.8 +/- 1.0 liters/min to 5.4 +/- 1.5 liters/min and an increase in mitral valve area from 0.86 +/- 0.24 cm2 to 2.41 +/- 0.54 cm2. The mean pulmonary artery pressure decreased from 37 +/- 13 mm Hg to 27 +/- 12 mm Hg and the pulmonary vascular resistance decreased from 307 +/- 181 to 238 +/- 122 dynes/s/cm-5. Symptomatic improvement occurred in 272 of the 285 (95%) patients. There were 3 procedure-related deaths (1%). Postdilatation mitral regurgitation was not significant in most patients. Therefore, this procedure can be performed at a low risk with effective results and a fast recovery.

Protection of implanted pacemakers from excessive electrical energy of D.C. shock

Abstract Studies were performed on implanted pacemakers subjected to electroshock in 55 dogs. With exposure to 400 w.sec., electrical energies of 18 ma. and 29 v. were recorded in the epicardial lead system and energies of 1,000 ma. and 350 v. recorded in the epicardial ground plate lead systems. One of 20 Medtronic pacemakers having the bipolar lead system configuration was damaged in the experiment. Three of five Cordis Corporation pacemakers without protective zener diode circuitry were damaged. The addition of shunt diodes in the Cordis pacemaker input/output terminals provided a significant measure of protection. Implanted pacemakers may be made less vulnerable to electrical shock by incorporating components with adequate transient breakdown ratings and by employing electrodes of small surface area, small interelectrode distance and electrode orientation perpendicular to the defibrillator paddles.

Sequential left ventricular function studies before and after pericardiectomy for constrictive pericarditis: Delayed resolution of residual restriction

Abstract A patient with constrictive pericarditis was studied 5 days before and 50 days and 13 months after extensive pericardiectomy. Functional data were derived from measurement of intracardiac pressure and left ventricular volume. Before operation the left ventricle was characterized by both systolic and diastolic unloading due to volume restriction. Complete anterior and lateral decortication was accompanied by minimal early clinical improvement. Catheterization studies reflected persistent severe biventricular restriction. A year after operation, marked clinical improvement was accompanied by studies revealing resolution of the restrictive elements.

Cholelithiasis: A frequent complication of artificial heart valve replacement

The results of this investigation reveal that 39 per cent of patients in a study group of 46 patients with heart valve prostheses had gallstones if they survived 18 months or longer following valve replacement. In contrast, the prevalence of gallstones in a general population of autopsied rheumatic heart disease patients, including those who had been operated for severe valvular heart disease and had not survived for more than one month, was only 12 per cent. These findings suggest that gallstones are a frequent late complication of heart valve replacement.

Thromboembolism in mitral porcine valve recipients.

A low incidence rate of thromboembolism has been reported in mitral porcine valve recipients. In contrast, 5 of 22 single mitral porcine valve recipients (23 percent) followed up in our clinic for a mean of 16 months had thromboembolic events. All patients but one were receiving long-term anticoagulant therapy. One thromboembolic event resulted in death, three in permanent neurologic deficits and one in a peripheral arterial occlusion. All five patients with emboli had atrial fibrillation and left atrial enlargement. Three had thromboembolic events before porcine heart valve implantation. In addition, five mitral porcine valve recipients who were not receiving anticoagulant therapy were examined at autopsy. Thrombus was identified in the left atrium in three patients, at the tissue-valve interface (sewing ring) in two, on the porcine valve cusps in one and in the right atrium in one. Factors influencing thrombus formation such as left atrial enlargement, atrial fibrillation and a prosthetic device are present after mitral porcine valve implantation and are indications for long-term anticoagulation therapy.

Distortions in infant electrocardiograms caused by inadequate high-frequency response

Frank lead ECGs from infants were studied for frequency content by introducing low-pass filters of 50, 75, 100, and 150 150 Hz bandwidths before obtaining computer measurements. Results indicated that a minimum bandwidth of 100 Hz is required to avoid amplitude error of 10 per cent or greater. This bandwidth requierement is essentially the same as that required for adult ECGs despite the fact that infant QRS durations are usually about half those of adults. Although the average infant ECG spectrum is likely to contain higher frequencies than the average adult ECG spectrum, duration values for Q, R, and S waves overlap in these populations to such an extent that bandwidth requirements are practically identical.

Diagnostic features of right ventricular myxoma

The clinical diagnostic features of right ventricular myxoma are described in a recent patient and related to the 15 cases previously reported. The presence of a pulmonic systolic ejection murmur with a delayed (120 to 140 msec.) and accentuated pulmonic second sound, or calcification in the region of the right ventricular outflow tract should suggest this lesion. Cardiac catheterization with angiocardiography in diagnostic. Ga scanning may assist in the diagnosis and followup after surgical removal of the myxoma. Early surgical removal will avoid the possibility of sudden death.

Computer analysis of changes in frank vectorcardiograms of 666 normal infants in the first 72 hours of life

Frank vectorcardiograms (VCGs) were collected on magnetic tape for 666 normal newborn infants at 1, 6, 12, 24, 36, 48, 60, and 72 hours after birth and analyzed by computers. The final total included 1,337 VCGs for white babies and 413 for blacks. No previous report has been made for the normal neonate with such a large sample, and no previous substantiation exists of possible age or sex differences at this early age. This study establishes a statistically significant change in vectorcardiographic patterns over the first three days, specifically in the measurements P duration, QRS duration, maximal spatial QRS amplitude, S in lead x, and T in lead z, as well as for several time-normalized QRS vectors. (P less than or equal to .005.) Racial differences were significant for T waves in lead z. This study supports the use of vectorcardiographic standards sensitive to the age of the newborn as well as to race.

Complete heart block: Prognostic value of electrocardiographic features and clinical complications☆

Abstract Eighty of 98 patients with acquired complete heart block are presented and discussed with respect to the effect on prognosis of age, etiology, presence of cardiac and extracardiac complications and electrocardiographic data. In this series of 48 control and 32 paced patients, mortality was adversely affected by myocardial infarction, uremia, shock, diabetes, a ventricular rate below 30/min., and Stokes-Adams attacks. Mortality was not affected by changing block, duration of the QRS interval, or the presence of cardiac failure. The prognosis in complete heart block was improved by pacing except in the presence of severe renal or metabolic complications.

Clinical Experience With the Smeloff-Cutter Aortic Valve Prosthesis: An 8-Year Follow-Up Study

A total of 46 patients who survived aortic valve replacement with the present model Smeloff-Cutter prosthesis between 1968 and 1973 were followed up postoperatively. All patients received oral anticoagulant therapy. The average age at implantation was 44 +/- 13 (mean +/- standard deviation) years; 36 patients were male and 10 were female. The valve damage was caused by rheumatic disease in 19 (41 percent), infective endocarditis in 14 (30 percent), congenital heart disease in 7 (15 percent) and other factors in 6 (13 percent). Late death occurred in eight patients (17 percent). All available patients were followed up until December 1976. During the 8 years of follow-up study, seven patients, including four heroin addicts, had postoperative endocarditis (15 percent); five of the seven had cerebral involvement, possibly from septic emboli. Four patients were reoperated on; three had active endocarditis and one had a high transvalve pressure gradient. The mean follow-up time was 4.9 years per patient. Of the 38 living patients, 33 have functional improvement and are still being followed up. Only one patient had a bland embolism to a systemic artery. No ball variance or other types of material failure have been detected. Although the chronic aspects of valve disease remain after prosthetic valve replacement, the Smeloff-Cutter aortic prosthesis deserves strong consideration when selecting a rigid prosthesis for aortic valve replacement.