Chun-Ho Cheng

A prospective study of elective stenting in unprotected left main coronary disease.

The standard treatment of left main coronary artery (LMCA) disease has been bypass surgery (CABG). Recent reports suggested that stenting of LMCA disease might be feasible. From January 1995 to April 1998, we carried out a prospective study of elective stenting of unprotected LMCA disease to evaluate its immediate and long‐term results. Of 61 consecutive patients with unprotected LMCA disease, 6 were excluded. Acute procedural success was 100% for the remaining 55 patients, without any complications such as stent thrombosis, myocardial infarction, CABG, or death. During a mean follow‐up of 16.1 ± 9.6 months, 11 patients (20%) had symptomatic recurrence, between 2 to 6 months after their procedure. Seven patients underwent CABG, two had repeat intervention, one continued with medical therapy, and one died before planned angiography. There was no late sudden death. Forty‐four patients (80%) remained asymptomatic. We conclude that elective stenting may be a safe alternative to CABG in unprotected LMCA disease. Cathet. Cardiovasc. Intervent. 46:153–159, 1999.

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.

Improvement in exercise performance and hemodynamics by labetalol in patients with idiopathic dilated cardiomyopathy

Labetalol, a combined alpha- and beta-blocking agent, was administered to 12 patients (mean age 55 years) with idiopathic dilated cardiomyopathy to examine its effects on symptomatology and exercise performance. Studies were performed before treatment, after 8 weeks of placebo, and after 8 weeks of labetalol therapy in a randomized, crossover, double-blind design. The mean (+/- SEM) dose of labetalol for the group was 275 +/- 29 mg. Compared to treatment with placebo, the maximum duration of symptom-limited exercise was significantly prolonged with labetalol (580 +/- 72 seconds to 683 +/- 71 seconds; p less than 0.005). Both the resting and peak exercise heart rate and systolic blood pressure were significantly reduced. Ascending aortic blood flow velocity was also measured by continuous-wave Doppler technique during exercise. Compared to placebo, treatment with labetalol conferred no significant change in cardiac output at rest but significantly improved cardiac output at maximum exercise (14 +/- 3%; p less than 0.001). Doppler-derived peak aortic flow velocity, acceleration, and flow velocity integral were also significantly improved at maximum exercise. Systemic vascular resistance, as derived from mean blood pressure/cardiac output, was reduced by 12 +/- 3% and 16 +/- 3% at rest and at maximum exercise, respectively. New York Heart Association functional class was improved (3.2 +/- 0.2 to 2.2 +/- 0.3; p less than 0.005). No major side effects from labetalol were encountered. Thus labetalol improves symptomatology, exercise capacity, and exercise hemodynamics and reduces systemic vascular resistance in patients with idiopathic dilated cardiomyopathy.

Rate Responsive Pacing with a Minute Ventilation Sensing Pacemaker during Pregnancy and Delivery

A minute ventilation sensing rate responsive pacemaker was implanted in a 29‐week pregnant woman with symptomatic complete atrioventricular (AV) block under echocardiographic and electrocardiographic (EGG) guidance. Satisfactory rate responses during a submaximal treadmill exercise test and daily activities were achieved. The course of pregnancy and cesarean section is discussed. During the cesarean section and after the delivery of the baby, changes in the ventilator settings confirmed that the pacing rate was closely correlated with both the tidal volume (r = 0.94, P<0.02) and the respiratory rate (r = 0.93, P < 0.05).

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)

Pacemaker mediated tachycardias in single chamber rate responsive pacing.

LAU, C.‐P., ET AL.: Pacemaker Mediated Tachycardias In Single Chamber Rate Responsive Pacing. Although pacemaker mediated tachycardias are classically associated with dual chamber pacemakers, single chamber rate responsive pacemakers are also susceptible to such tachycardias under special circumstances. A unipolar activity sensing rate responsive pacemaker (Activitrax 8403) was implanted in an 83‐year‐old man with complete atrioventricular block. The pacemaker was programmed at an output of 5 V, activity threshold medium, rate response 5, and lower and upper rates of 70 and 125 beats/min, respectively. He presented with palpitations at rest and muscle twitching of the pacemaker pocket 4 months after implantation. Examination confirmed that the pacemaker had flipped over, resulting in pocket pacing which in turn activated the activity sensor, resulting in a rate response. The increase in pacing rate lead to a higher frequency of pocket pacing, thus leading to positive feedback increase in rate. With the patient at rest, pacemaker mediated rates were 106, 91, and 74 beats/min at low, medium and high thresholds, respectively. Decreasing the output to 2.5 V eliminated pocket pacing and the tachycardia. As a result of the reversal of the pacemaker, a similar rate response during exercise could only be achieved at a more sensitive rate responsive setting. Thus, pacemaker mediated tachycardia can complicate pacemaker “flipping” in single chamber activity sensing rate responsive pacemakers. Methods for the avoidance and treatment of pacemaker flipping are discussed. A review of other sensor mediated tachycardias is also presented.

Hypocalcemic Heart Failure in End-Stage Renal Disease

A 37-year-old woman presented with hypocalcemic heart failure complicating end-stage renal disease. Heart failure persisted despite conventional therapy but improved after correction of hypocalcemia. Continuous monitoring of left ventricular function by radionuclide study during calcium replacement showed dramatic improvement. Our case showed that hypocalcemia could be a rare but reversible cause of frank heart failure in uremic patients.

Importance of Heart Rate Modulation on the Cardiac Hemodynamics During Postexercise Recovery

The influence of heart rate changes on the recovery of cardiac hemodynamics and lactate clearance after exercise was studied in nine patients with complete atrioventricular (AV) block treated with programmable pacemakers. A preliminary treadmill exercise test in which the pacing rate was externally increased stepwise from 70 to 230 bpm was performed fo determine the maximum exercise duration. Two exercise tests involving an equal amount of exercise load were performed, the pacing rate was either programmed to the basic rate (abrupt decay) or gradually (modulated decay) immediately after exercise termination. Compared with abrupt decay, modulated decay resulted in a higher mean arterial pressure (100 ± 4 mmHg vs 91 ± 5 mmHg, P ± 0.05) and diastolic pressure (76 ± 4 mmHg vs 59 ± 4 mmHg, P < 0.001) immediately on exercise termination. Immediately after exercise and during modulated decay, cardiac output (represented by Doppler derived minute distance] declined gradually and was determined mainly by a higher pacing rate without significant changes in stroke volume. On the other hand, minute distance fell abruptly during abrupt decay (996 ± 107 m at peak exercise and 561 ± 88 m immediately after a rate change at exercise termination, P < 0.01) with a corresponding abrupt increase in systemic vascular resistance. This was later compensated by a gradual increase in stroke volume during the recovery period. The cumulative cardiac output between the two rate changes equalized at the 4th minute of recovery. Abrupt decay was associated with a higher recovery atrial rate (109 ± 5 bpm versus 102 ± 5 bpm at the fifth minute of recovery, P < 0.01) and a higher peak velocity of ascending aortic flow, both suggestive of an enhanced sympathetic level during this mode of recovery. There is a trend toward a higher peak arterial lactate level during abrupt decay, although the overall lactate clearance rates between the two decay modes were similar. Most patients preferred the modulated decay. In conclusion, rate modulation at exercise termination produced more gradual hemodynamic changes compared with abrupt decay. Cardiac hemodynamics was maintained by a compensatory increase in stroke volume and an increase in sympathetic activities after a latent period. Independent of the form of rate modulation, a fixed amount of cardiac output appears necessary to facilitate postexercise recovery after a given workload.