James Leitch

Cardiac Event Recorders Yield More Diagnoses and Are More Cost-effective than 48-Hour Holter Monitoring in Patients with Palpitations: A Controlled Clinical Trial

Palpitation is a common symptom that sometimes results from a substantial cardiac arrhythmia. Establishing the cause of palpitations may be difficult because historical clues are not always accurate [1]. A 24-hour ambulatory (Holter) monitor is usually used, but the yield of this instrument is low in patients whose symptoms occur infrequently [2-5]. Another instrument used to study palpitations is a transtelephonic post-event recorder. These hand-held devices are given to patients and are applied to the chest when symptoms occur. The patient presses a button to record about 30 seconds of the cardiac rhythm, which is stored in the memory of the device. The recording is later transmitted over the telephone for printing and interpretation. Although this instrument has been available for many years, concerns have been expressed about the quality of recording and the extent to which an unselected group of patients can provide diagnostic recordings. Because no randomized, controlled trials have compared these devices with Holter monitoring, we compared the yields of Holter monitoring with those of event recorders in diagnosing palpitations in an unselected population. Methods Patients We considered for our study all 634 men and women referred to the cardiovascular unit at the John Hunter Hospital for Holter monitoring. We excluded patients being monitored for silent ischemia (7%), assessment of therapy (18%), syncope (18%), or other research studies or inpatient monitoring (8%); patients considered too old, too feeble, or too young to use the event monitor (16%); and patients who had previously had Holter monitoring for their symptoms (16%). The remaining 108 patients (17%) were eligible for the study. One investigator interviewed eligible patients to confirm that their symptoms were palpitations. We asked patients to estimate how frequently they had symptoms, the length of their longest attack, whether their palpitations were regular, and whether they smoked or had a history of hypertension or ischemic heart disease. Each patient provided informed consent, and the Hunter Health Service ethics committee approved the study. Our study was a randomized crossover trial. Each patient was randomly allocated to have either 48 hours of Holter monitoring (Marquette Electronics, Sydney, New South Wales, Australia) or an event monitor (Aerotel, Israel; Medtronic, Minneapolis, Minnesota). The patient kept the event monitor until two recordings were obtained during symptoms or until 3 months had passed. After the first monitor was returned, the patient was given the other device. During Holter monitoring, patients were asked to record in a diary when their index palpitation symptoms occurred during the 48-hour recording period. Patients also recorded the symptoms associated with their palpitations, including dizziness, nausea, shortness of breath, chest discomfort or pain, and arm pain. We defined these criteria before the study. To check the correctness of the interpretation of arrhythmias, we used a full-disclosure method that allowed review of all 48 hours of electrogram recording. A cardiologist blinded to the results from the event recorder read the reports and electrocardiogram printouts of arrhythmias during symptomatic and asymptomatic periods. Tracings for the event recorder were read by another cardiologist who was also blinded to patient data and results of 48-hour Holter monitoring. End Points The primary end point was an electrocardiogram rhythm strip obtained while symptoms occurred that would establish a cardiac or noncardiac cause of the symptoms. The secondary end point was a clinically significant cardiac arrhythmia defined before the study as symptomatic sustained supraventricular tachycardia (supraventricular rate, more than 15 beats/min), atrial fibrillation or flutter, sustained ventricular tachycardia (ventricular rate, more than 10 beats/min), sinus pause longer than 3 seconds, non-Wenckebach second-degree heart block, or third-degree heart block. Statistical Analysis We analyzed the data using the STATA program (Stata, College Station, Texas). Because all patients received both devices, we used an exact binomial test of untied pairs to determine the statistical significance of the primary and secondary end points [6]. Cost-Effectiveness Analysis We calculated incremental cost-effectiveness ratios (the additional cost per additional health outcome) of event monitors compared with Holter monitors for the primary and secondary end points. All costs were in 1994-1995 Australian dollars. The analysis was based on a time horizon of 21.5 weeks, which we estimated to be the period during which the study cohort of 43 patients (who could use either monitor) would present for monitoring. Assuming that the event monitors would be given to patients for 6 weeks, approximately 13 event monitors were required to monitor these 43 patients for 21.5 weeks. We used a societal perspective in our analysis and estimated direct medical costs of capital, labor, and consumable goods and nondirect medical costs of telephone calls (event monitors only). We excluded overhead costs for central administration, cleaning, heating, and so forth (direct medical costs) and for travel expenses (direct nonmedical costs) on the assumption that these variables would not differ between the devices. We calculated equivalent annual costs for capital using an annuitization procedure in which we assumed an expected life span of 5 years for both monitors and a 5% discount rate. The five Holter monitors and the analysis system in our unit cost approximately

Reduction in defibrillator shocks with an implantable device combining antitachycardia pacing and shock therapy

106 193; this results in an equivalent annual cost of

VDD pacing at short atrioventricular intervals does not improve cardiac output in patients with dilated heart failure.

24 528. Because Holter equipment is used for purposes other than investigating palpitations, we apportioned joint costs on the basis of the percentage of use attributed to patients with intermittent palpitations (17%). We apportioned an annual service cost, estimated to be 4.1% of the capital cost, on the same basis. The cost of 13 event monitors was estimated to be

Randomized trial of a hospital-based exercise training program after acute myocardial infarction: Cardiac autonomic effects

6500 (Micromedical Industries, Labrador, Queensland, Australia), which resulted in an annual equivalent cost of

QT dispersion does not predict early ventricular fibrillation after acute myocardial infarction

1561. We estimated labor costs for technicians, secretaries, and cardiologists according to time and motion for the last five patients investigated. Our technicians spent an average of 113 minutes to explain how to use, put on, and remove the Holter monitor and how to analyze and download the tapes. Thirty-five minutes was needed to explain the event recorders and to prepare the rhythm strip for reporting. A cardiologist could interpret the Holter monitor recordings in about 16 minutes and could interpret the event monitor recordings in 2 minutes; the respective times for secretarial work were 10 minutes and 5 minutes. We assigned a value to these services using wages that were positively adjusted for annual and sick leave, superannuation entitlements, and workers compensation premiums. We assessed the robustness of the results in multiway sensitivity analyses that examined the changes in the discount rate (0% and 10%), a 20% increase and decrease in service and labor costs, and a reduction of the proportion of Holter monitor costs attributed to Holter monitor use from 17% to 10%. The effectiveness was also varied by the 95% CIs. Results Of the 108 eligible patients, we asked 45 (40%) to participate in the study. We did not ask the others to participate because the two chief investigators were not available to interview them. Of the 45 patients asked, 43 (96%) completed the study. Two persons withdrew before receiving the event monitor because the Holter monitor leads were too uncomfortable. Thirty-eight participants (88%) were women, and the mean age of all patients (SD) was 45 19 years. Thirty-four patients (81%) reported that palpitations occurred at least every 2 weeks, and 24 (56%) believed that their palpitations were regular; the average estimate of the longest attack was 74 159 minutes. The mean resting pulse rate was 76 15 beats/min; systolic blood pressure was 131 26 mm Hg; and diastolic blood pressure was 77 12 mm Hg. Four patients reported a history of ischemic heart disease, 14 (33%) reported a history of hypertension, and 7 (16%) were smokers. Twenty-four patients (56%) were randomly allocated to receive the 48-hour Holter monitor before receiving the event recorder. Table 1 lists the results for the primary and secondary end points. Thirty patients (70%) sent in at least one electrocardiogram recorded by the event monitor while symptoms occurred. Two patients had a technically inadequate electrocardiogram recording transmission, but 1 patient subsequently sent two rhythm strips showing sinus rhythm. Therefore, 29 patients (67%) sent at least one recording from an event recorder that could be interpreted compared with the approximately one third of patients who obtained recordings during symptoms with the Holter monitor (P < 0.001). Furthermore, the Holter monitor detected no clinically significant arrhythmias. During event recorder monitoring, a clinically significant arrhythmia was documented in each of 8 patients (19%) (Table 1 and Table 2; Figure 1). Table 1. Number of Patients with an Electrocardiogram Recorded during Symptoms or with Clinically Significant Arrhythmia* Table 2. Types of Cardiac Rhythm from Electrocardiograms Recorded during Symptoms Figure 1. Electrocardiogram recording from an event recorder showing atrial fibrillation during palpitations. Of the 29 patients who recorded an electrocardiogram with the event monitor, 20 (69%) made two recordings and returned the monitor before the maximum 3 months allowed. For 13 patients (65%) who sent in two recordings, the two recordings showed the same rhythm. For the remaining 7 patients, the discordant rhythms were supraventricular tachycardia and sinus tachycardia in 3 patients (2 of whom had supraventricular tachycardia on the first recording), atrial flutter and ventricular premature beats

Long-term mechanical consequences of permanent right ventricular pacing: Effect of pacing site

Implantable defibrillators reduce the risk of sudden death in patients with malignant ventricular arrhythmias, but significant restriction in quality of life can occur as a result of frequent device activation. To determine if a device that provides both antitachycardia pacing and shock therapy can safely reduce the frequency of shocks after implantation, 46 consecutive patients undergoing initial implantation of a defibrillator were studied. In all patients, the implanted device provided antitachycardia pacing and shock therapy. Detected tachycardia characteristics and the results of therapy were stored in the devices memory. There were 42 men and 4 women, aged 26 to 71 years (mean 58.7 +/- 13.5). Left ventricular ejection fraction ranged from 13% to 67% (mean 32.2 +/- 13.4%) and 31 patients had experienced one or more episodes of cardiac arrest. Induced arrhythmias included sustained monomorphic ventricular tachycardia in 38 patients, nonsustained polymorphic ventricular tachycardia in 2 and ventricular fibrillation in 4. Over a total follow-up period of 255 patient-months (range 1 to 13, mean 6.1), 25 patients experienced spontaneous arrhythmic events. In 22 patients, 909 episodes of tachycardia were treated by antitachycardia pacing, which was successful on 840 occasions (92.4%). Acceleration of ventricular tachycardia by pacing therapy was estimated to have occurred 39 times. Syncope occurred once during pacing-induced acceleration of ventricular tachycardia. Forty-four episodes of tachycardia in seven patients were treated directly by shocks because of short tachycardia cycle length; 88% of all detected tachycardias were treated without the need for shocks. Four patients died from cardiorespiratory failure and one patient died suddenly without any detected tachyarrhythmia.(ABSTRACT TRUNCATED AT 250 WORDS)

Multiple accessory pathways in the Wolff-Parkinson-White syndrome as a risk factor for ventricular fibrillation

Atrial synchronous pacing with short, nonphysiologicai atrioventricular (AV) intervals has been reported to increase cardiac output in selected patients with severe dilated heart failure. The aim of this study was to determine the acute effect of atrial synchronous pacing with short AV intervals in a consecutive series of patients with dilated heart failure. Twelve patients with a mean ejection fraction of 21 %± standard error 2.5% were studied. Pacing catheters were placed in the high right atrium and right ventricular apex and a balloon flotation catheter in the pulmonary artery for measurement of cardiac output. Simultaneous transthoracic echocardiography was performed for measurement of left ventricular filling time and mitral regurgitation. In a randomized crossover design, measurements were made during VDD pacing at programmed AV intervals of 100 and 60 msec and during a control period in sinus rhythm. Left ventricular filling time increased at AV intervals of 100 and 60 msec (mean difference 37 ± 9 and 34 ± 11 msec, respectively, both P < 0.01 compared to control). Despite increases in ventricular filling time, stroke, and cardiac index declined with short atrioventricular intervals (at an AV interval of 60 msec, stroke index fell by 2.1 ± 0.5 mL/m2, P < 0.05 and cardiac index by 125 ± 45 mL/m2; P = NS). Heart rate was unchanged at both AV intervals (78 ± 4.9 at control, 78 ± 5.2 at 100 msec and 79 ± 4.9 beats/min at 60 msec; P = NS). The decrease in stroke index at an AV Interval of 60 msec was inversely related to control left ventricular filling time (r = 0.74; P = 0.01) and ejection fraction (r = 0.69; P = 0.02) and directly related to heart rate (r = 0.77; P < 0.01). The change in stroke index at an AV delay of 60 msec was also inversely related to the change in mitral regurgitation induced by pacing (r = 0.84; P = 0.01). Thus, in a group of patients with stable dilated heart failure, atrial synchronous pacing with short AV intervals did not improve cardiac output. The change in cardiac output with pacing was inversely related to baseline left ventricular function and to the change in mitral regurgitation induced by pacing.

Feasibility of an implantable arrhythmia monitor.

OBJECTIVES This study sought to determine whether a moderate intensity supervised exercise training program, performed immediately after an uncomplicated acute myocardial infarction, improves recovery in cardiac autonomic function compared with standard advice about activity at home. BACKGROUND Exercise training has beneficial effects on cardiac autonomic function and may improve prognosis after acute myocardial infarction. METHODS Thirty-nine male and 10 female patients, mean (+/-SE) age 57 +/- 1 years, with an uncomplicated acute myocardial infarction were randomized to either a 6-week moderate intensity supervised hospital-based exercise training program (exercise group) or to an unsupervised low intensity home walking program (control group). Outcome measures included changes in baroreflex sensitivity (phenylephrine bolus method) and heart rate variability (24-h Holter monitoring) and the endurance time at 85% of peak oxygen consumption. RESULTS At baseline, there were no significant differences in left ventricular ejection fraction (57 +/- 2% vs. 53 +/- 2%), frequency of anterior infarction (27% vs. 18%) and peak creatine kinase (1,256 +/- 170 vs. 2,599 +/- 295 IU) between the exercise and control groups. Baroreflex sensitivity (10.5 +/- 1.0 vs. 8.4 +/- 1.2 ms/mm Hg) and time domain measures of heart rate variability were also similar. After completion of the program, the exercise group exercised for a median of 15 min (interquartile range 12 to 25) at a workload of 104 +/- 7 W compared with 7 min (interquartile range 3.5 to 12) at a workload of 89 +/- 8 W in the control group (p < 0.01). There were significant (p < 0.001) improvements in baroreflex sensitivity and heart rate variability for the 49 patients combined but no differences between the exercise and control groups. Baroreflex sensitivity improved by 3.4 +/- 1.0 and 1.7 +/- 1.0 ms/mm Hg and the standard deviation of 24-h RR intervals by 36 +/- 6 and 40 +/- 10 ms, respectively (p > 0.1). CONCLUSIONS A hospital-based exercise training program increased endurance capacity but did not improve recovery of cardiovascular antonomic function after uncomplicated acute myocardial infarction.

Correlation Between the Ventricular Electrogram Amplitude in Sinus Rhythm and in Ventricular Fibrillation

Ventricular arrhythmias may be associated with increased QT dispersion (difference between maximum and minimum QT on standard 12‐lead ECG). We performed a case control study to determine if QT dispersion on the admission ECG could predict early VF after acute myocardial infarction. The cases were 24 patients with acute myocardial infarction (14 inferior, 8 anterior, and 2 lateral) with VF within 12 hours of admission. There were 24 control patients without VF matched for site of infarction and ST segment score (sum of ST segment elevation). VF occurred a median of 153 minutes (interquartile range 93–245) after onset of chest pain and 33 minutes (range 7–104) after initial ECG. QT (399 ± 37 and 394 ± 37), QT corrected (440 ± 38 and 429 ± 29), and QT dispersion (68± 20 and 66 ± 27) were similar in patients and controls. By design, ST score was similar (11 ± 9 vs 9 ± 5 mV), although a good match could not be obtained for three patients with extreme ST elevation. Patients with VF presented to the hospital earlier after the onset of chest pain (median 95 min [range 65–188] compared to 150 min [range 80–270], P= 0.05) and had a lower serum sodium (138 ± 2.4 vs 140 ± 2.5, P = 0.05) than controls. Thus, QT interval and QT dispersion, measured on the presenting ECG, did not predict early VF after myocardial infarction.

The limited utility of electrocardiography variables used to predict arrhythmia in psychotropic drug overdose

Optimal Right Ventricular Pacing Introduction: Long‐term right ventricular apical (RVA) pacing has been associated with adverse effects on left ventricular systolic function; however, the comparative effects of right ventricular outflow tract (RVOT) pacing are unknown. Our aim was therefore to examine the long‐term effects of septal RVOT versus RVA pacing on left ventricular and atrial structure and function.