Cheuk-Kit Wong

Beneficial effect of cholesterol-lowering therapy on coronary endothelium-dependent relaxation in hypercholesterolaemic patients.

Since hypercholesterolaemia is associated with impaired endothelium-dependent vasodilation, a study was conducted to find out whether cholesterol reduction will improve endothelial function in patients with hypercholesterolaemia and normal coronary arteries. 25 men (mean age 51 [SD 8] years) with total serum cholesterol > 6.2 mmol/L) and angiographically normal coronary arteries had their coronary vasomotor responses to intracoronary acetylcholine and nitroglycerin assessed by computer-assisted quantitative angiography at baseline and after 6 months of cholesterol-reducing diet and cholestyramine. Between baseline and follow-up mean total serum cholesterol level fell by 28.7 (SD 5.6)% (p < 0.001); mean low-density lipoprotein (LDL) cholesterol level by 35.6 (8.7)% (p < 0.001); and mean total cholesterol to high-density lipoprotein (HDL) cholesterol ratio by 29.4 (10.6)% (p < 0.001). Acetylcholine significantly reduced the mean segment diameter at baseline, by 21.7 (14.0)% (p < 0.01), but it increased the diameter at follow-up, by 6.16 (13.3)% (p < 0.01), the difference between the two occasions being significant (p < 0.001). Nitroglycerin significantly increased the mean segment diameter, both at baseline, by 18.7 (11.5)% (p < 0.01), and at follow-up, by 19.3 (12.1)% (p < 0.01), the difference between the two responses being not significant. At baseline total cholesterol and LDL cholesterol did not correlate with acetylcholine response, but they did at follow-up (total cholesterol, r = 0.67, p < 0.01; LDL cholesterol, r = 0.64, p < 0.01). Impairment of endothelium-dependent (acetylcholine-induced) dilation of the epicardial coronary arteries in hypercholesterolaemic patients with angiographically normal coronary arteries is thus reversible by reducing serum cholesterol. In addition, the degree of impairment of acetylcholine-induced vasomotor response is related to the cholesterol concentrations after therapy.

Association between antiphospholipid antibodies and cardiac abnormalities in patients with systemic lupus erythematosus

Abstract purpose : Although the antiphospholipid antibodies are well recognized to be associated with thrombosis, recurrent abortion, and thrombocytopenia in patients with systemic lupus erythematosus (SLE), their relationship with cardiac disease is less clear. The purpose of this study was to evaluate the association between antiphospholipid antibodies and cardiac abnormalities in patients with SLE. patients and methods : A total of 75 consecutive SLE patients and 60 healthy sex- and age-matched control subjects were evaluated in a case-control study. All participants underwent M-mode, two-dimensional, and Doppler echocardiography. Antiphospholipid antibodies levels were assayed in each patient. The prevalence of antiphospholipid antibodies in patients with and without echocardiographic abnormalities was compared. results : Compared with the control group, SLE patients had significantly more pericardial abnormalities, left ventricular hypertrophy, left atrial enlargement, left ventricular dysfunction and verrucous valvular thickening, global valvular thickening with dysfunction, and mitral and aortic regurgitation. Among these abnormalities, antiphospholipid antibodies were significantly associated with isolated left ventricular (global or segmental) dysfunction (four of five positive; p conclusion : Valvular lesions and myocardial dysfunction are associated with elevated antiphospholipid antibodies. This study has important implications for the pathogenic role of antiphospholipid antibodies in relation to these cardiac abnormalities.

Doppler echocardiographic evaluation of left ventricular diastolic function in patients with systemic lupus erythematosus.

Subclinical myocardial involvement frequently occurs in patients with systemic lupus erythematosus (SLE). In this study, left ventricular diastolic function was assessed in 58 patients (54 female and 4 male; mean age 32 +/- 11 years) and in 40 sex-matched and age-matched healthy control subjects (37 female and 3 male; mean age 33 +/- 9 years) by means of pulsed Doppler echocardiography. All subjects had no clinical evidence of overt myocardial disease or abnormal left ventricular systolic function. Compared with the control group, patients with SLE had significantly prolonged isovolumic relaxation time (62 +/- 12 vs 80 +/- 14 msec; p less than 0.01), reduced peak early diastolic flow velocity (peak E) (82 +/- 18 vs 76 +/- 16 cm/sec; p less than 0.05), increased peak late diastolic flow velocity (peak A) (45 +/- 7 vs 53 +/- 8 cm/sec; p less than 0.01), reduced E/A ratio (1.81 +/- 0.32 vs 1.46 +/- 0.29; p less than 0.001), and lower deceleration rate of early diastolic flow velocity (EF slope) (489 +/- 151 vs 361 +/- 185 cm/sec2; p less than 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)

Cardiac abnormalities in systemic lupus erythematosus: a prospective M-mode, cross-sectional and Doppler echocardiographic study

A prospective M-mode, cross-sectional and Doppler echocardiographic study was performed on 75 patients with systemic lupus erythematosus and 60 sex- and age-matched control subjects. Compared with the control group, patients with lupus had an increased prevalence of echocardiographic abnormalities. These included pericardial effusion and/or thickening (37%), left ventricular hypertrophy (12%), global left ventricular hypokinesis (5%), segmental abnormalities of left ventricular wall motion (4%), right ventricular enlargement (4%), focal verrucous valvar thickening (12%), gross valvar thickening and dysfunction (8%), mitral regurgitation (25%) and aortic regurgitation (8%). Two patients with gross mitral valvar thickening and dysfunction subsequently underwent valvar replacement. Correlation between echocardiographic abnormalities and clinical parameters showed that pericardial effusion was significantly associated with pericardial pain (P less than 0.05) and active disease (P less than 0.001), and left ventricular hypertrophy with systemic hypertension (P less than 0.05). Thus, there was a high prevalence of cardiac abnormalities, especially pericardial and valvar lesions, in patients with systemic lupus erythematosus. Echocardiography is invaluable in identifying these abnormalities and should be used routinely for cardiac evaluation of these patients.

A randomized double-blind crossover study comparing the efficacy and tolerability of flecainide and quinidine in the control of patients with symptomatic paroxysmal atrial fibrillation.

Patients with paroxysmal atrial fibrillation (PAF) are prone to recurrence. We compared the efficacy and tolerability of flecainide acetate in the control of PAF by means of conventional treatment with quinidine in 19 patients without structural heart disease. A randomized, placebo-controlled, crossover protocol consisting of 8 weeks of treatment with either agent was used. The recurrence of PAF was documented in a symptom diary and confirmed by event ECG recording. Complete control of symptoms was achieved in 4 of 19 and 2 of 11 of patients with flecainide and quinidine, respectively. Both agents prolonged the time to the first recurrence and significantly reduced the total duration of PAF recurrence by 40% and 47%, respectively (p less than 0.05 compared with placebo). Compared with quinidine, flecainide significantly reduced the frequency of recurrence and the rate of PAF during a recurrent episode. However, treatment with flecainide was associated with a higher incidence of symptomatic sinus pauses and visual disturbances compared with a higher incidence of gastrointestinal side effects with quinidine. During a follow-up period of 32 months, satisfactory control was achieved in 74% of patients with the use of these two antiarrhythmic agents.

Superior Cardiac Hemodynamics of Atrioventricular Synchrony Over Rate Responsive Pacing at Submaximal Exercise: Observations in Activity Sensing DDDR Pacemakers

LAU, C.‐P., ET AL.: Superior Cardiac Hemodynamics of Atrioventricular Synchrony Over Rate Responsive Pacing at Submaximal Exercise: Observations in Activity Sensing DDDR Pacemakers. The relative hemodynamic profile between dual chamber pacing (DDD) and activity sensing rate responsive pacing (VVIR) was compared in ten patients with dual chamber rate responsive pacemakers (Synergist 11). With a double blind, randomized exercise protocol, DDDR pacemakers were programmed into VVI, VVIR, and DDD (AV interval 150 msec) modes and in seven patients the test in the DDD mode was repeated with the AV interval programmed at 75 msec. A treadmill exercise test of 6‐minutes duration (2 stages, Stage 1 at 2 mph, 0% gradient and Stage II at 2 mph, 15% gradient) was performed at each of the programmed settings, with a rest period of 30 minutes in between tests. Cardiac output was assessed using continuous‐wave Doppler sampling ascending aortic flow and expressed as a percentage of the value achieved during VVI pacing. During exercise, pacing rate between DDD and VVIR pacing was similar but was higher with DDD at the first minute of recovery (91 ± 4vs 81 ± 3 beat/min, respectively). Cardiac output was significantly higher at rest, during low level exercise, and recovery with DDD pacing compared with VVIR pacing (resting: 21 ± 14 vs ‐2 ± 7%; Stage I: 36 ± 6 vs 16 ± 7%; Stage II: 25 ± 15 vs 10 ± 8%; recovery: 26 ± 12 vs 4 ± 9%; p < 0.05 in all cases). Systolic blood pressure was significantly higher during low level of exercise in the DDD mode. Shortening of the AV interval to 75 msec did not significantly affect cardiac output during exercise, but cardiac output after exercise was reduced (2 ± 6 vs 23 ± 6% at an AV interval of 150 msec, p < 0.02). By enhancing the stroke volume, DDD pacing improves cardiac hemodynamics at rest, during low level exercise, and early postexercise recovery.

A Comparative Evaluation of a Minute Ventilation Sensing and Activity Sensing Adaptive‐Rate Pacemakers During Daily Activities

Most studies evaluating the rate response of adaptive‐rate pacemakers have been based on treadmill or bicycle exercise. These studies disregard the fact that few pacemaker recipients voluntarily undertake such activities. The rate responses of nine patients (mean age 62 years, range 33 79 years) with implanted minute ventilation sensing (Meta) pacemakers were studied. The indications for pacing were complete heart block (seven patients), six sinus syndrome (one patient), and five nodal disease (one patient). Significant improvement in maximum distance covered during a 12‐minute walking test was observed in the rate adaptive compared to the VVI pacing mode (989 ± 104 vs 921 ± 90 m. P < 0.02). The rate responses of this pacemaker during daily activities were recorded with telemetry during a variety of structured daily activities. The rate responses were also compared to those of an externally attached Activitrax pacemaker in each patient and to a group of ten age and sex matched volunteers. For less strenuous activities such as walking, descending stairs, washing, and bed making, both pacemakers achieved adequate rate responses compared to normal subjects. For more strenuous activities, the Activitrax pacemaker failed to achieve an adequate rate response. For example. the pacing rate achieved on ascending stairs was lower than that achieved on descending stairs (92 ± 3 vs 102 ± 3 bpm, P < 0.02). The direction of rate responses was more appropriate for the Meta pacemaker. Similar to the normal subjects, the maximum rate was reached before the end of an activity with the Activitrax pacemaker. A significant delay was observed with the Meta pacemaker and the rate response was achieved during the recovery period of some activities (e.g., maximum pacing rate was achieved at 45 ± 35 sec after ascending stairs with the Meta pacemaker). In conclusion, the Meta pacemaker improved submaximal exercise capacity. This study suggests the two different rate adaptive pacemakers differed in their proportionality and speed of rate responses.

Usefulness of labetalol in chronic atrial fibrillation

Beta-adrenergic blocking agents are useful in controlling excessive ventricular rate in chronic atrial fibrillation (AF) but often reduce exercise capacity. To investigate the advantage of labetalol--a unique beta blocker with alpha-blocking property--in chronic AF, 10 patients without underlying structural heart disease were studied with treadmill test, 12-minute walk and 24-hour ambulatory electrocardiographic monitoring. Patients were randomized and crossed over to receive 4 phases of treatment (placebo, digoxin, digoxin with half-dose labetalol, and full-dose labetalol). Exercise durations were 14.1 +/- 1.5, 14.2 +/- 1.5, 16.1 +/- 1.1 and 15.6 +/- 1.1 minutes, respectively, indicating that labetalol did not reduce exercise tolerance. Although digoxin had no advantage over placebo in controlling maximal heart rate (177 +/- 2 vs 175 +/- 3 beats/min), labetalol, both as monotherapy or as an adjunct to digoxin, was advantageous (156 +/- 4 vs 177 +/- 2 beats/min, p less than 0.01, and 154 +/- 4 vs 177 +/- 2 beats/min, p less than 0.01, respectively). The rate-pressure product was consistently lowered by labetalol at rest and during exercise. At peak exercise, the addition of labetalol to digoxin reduced the maximal rate-pressure product achieved from 30,900 +/- 1300 to 24,100 +/- 2,000 mm Hg/min (p less than 0.01) and the maximal rate-pressure product was lowest with full-dose labetalol (22,300 +/- 1,600 mm Hg/min). During submaximal exercise on treadmill or during the 12-minute walk, the combination of labetalol and digoxin produced the best heart rate control, whereas labetalol monotherapy was comparable to digoxin therapy.(ABSTRACT TRUNCATED AT 250 WORDS)

Hypocalcemic myocardial dysfunction: short- and long-term improvement with calcium replacement.

The effects of short- and long-term calcium replacement on myocardial function in six asymptomatic patients (age 48 +/- 3, mean +/- SEM) with hypocalcemia complicating surgical hypoparathyroidism were studied. Cardiac output was determined by ascending aortic continuous wave Doppler assessment and was measured as minute distance. During intravenous calcium replacement at rest, ascending aortic minute distance increased from 6.75 +/- 1.10 to 9.17 +/- 1.29 m as the calcium level rose from 1.76 +/- 0.08 to 2.06 +/- 0.19 mmol/L without changes in heart rate and blood pressure (p less than 0.01). The peak velocity and acceleration of blood flow derived from Doppler measurement showed a similar rise during calcium infusion. Symptom-limited cycle ergometry was performed before and 3 months after normalization of calcium by long-term oral therapy. Although the resting cardiac output was unchanged, the maximum cardiac output at peak exercise also increased from a minute distance of 11.58 +/- 1.84 to 15.37 +/- 2.28 m (p less than 0.05), together with an increase of maximum heart rate from 136 to 149 beats/min (p less than 0.05). Exercise duration was also prolonged from 11.9 +/- 2.9 to 13.0 +/- 2.8 minutes. Thus hypocalcemia impairs cardiac performance, but this impairment is reversible with calcium replacement.

An arteriovenous fistula from an aberrant right subclavian artery to the superior caval vein in a congenitally myxoedematous adult

A 52-year-old woman with congenital myxoedema presented with congestive heart failure and a continuous heart murmur. On cardiac catheterization, an aberrant right subclavian artery was found which supplied an arteriovenous malformation. Her heart failure, however, was secondary to concomitant severe aortic regurgitation which was clinically masked by the signs of the fistula. To our knowledge, a congenital arteriovenous malformation arising from an aberrant subclavian artery has not been reported in the adult.