Differences in heart rate dynamics before the spontaneous onset of long and short episodes of paroxysmal atrial fibrillation

BACKGROUND

Altered heart rate (HR) dynamics precede the spontaneous onset of atrial fibrillation (AF), but the factors related to the perpetuation and duration of paroxysmal AF episodes are not well established. This study was designed to test the hypothesis that HR dynamics preceding the onset of (AF) may influence the duration of AF.

METHODS

Traditional time and frequency domain HR variability indices, along with a short-term fractal scaling exponent (alpha(1)) and approximate entropy (ApEn), were analyzed in 20-minute intervals before 92 episodes of spontaneous paroxysmal AF in 22 patients without structural heart disease. AF episodes were divided into two groups according to the duration of the arrhythmia episodes.

RESULTS

The high-frequency (HF) spectral component in normalized units (nu) of heart rate variability was higher and low-frequency (LF) component lower before long (> 200 s, n = 41) compared to short (< 200 s, n = 51) AF episodes (HF nu; 40.1 +/- 14.8 vs 31.5 +/- 16.4, P < 0.0001 and LF nu; 59.9 +/- 14.8 vs 68.5 +/- 16.4, P < 0.0001). Short-term scaling exponent values also were lower before long compared to short AF episodes (e.g., alpha(1); 1.12 +/- 0.21 vs 1.24 +/- 0.23, P < 0.0001). Women had a larger number of long AF episodes than men, but the duration of AF was not related to any other clinical or demographic features or antiarrhythmic medication.

CONCLUSION

Increased HF oscillations and decreased short-term correlation properties of R-R intervals, reflecting altered sympathovagal balance before the onset of AF, predispose to perpetuation of spontaneous arrhythmia episodes in patients with vulnerability to paroxysmal AF and without structural heart disease.

Epidural infusion of bupivacaine and fentanyl reduces perioperative myocardial ischaemia in elderly patients with hip fracture--a randomized controlled trial

BACKGROUND

Perioperative myocardial ischaemia is an important risk factor for cardiac morbidity and mortality after noncardiac surgery. The impact of analgesic management on the incidence and severity of cardiac ischemia was studied in 77 elderly patients undergoing surgical treatment of traumatic hip fracture.

METHODS

After hospital admission and written consent, patients were randomised to conventional analgesic regimen (intramuscular oxycodone, OPI group) or continuous epidural infusion of bupivacaine/fentanyl (EPI group). The analgesic regimens were started preoperatively. Patients were operated under spinal anaesthesia and the treatments were continued three days postoperatively. ECG was continuously recorded. ST segment depression of > or = 0.1 mV or elevation of > or = 0.2 mV lasting > or = 1 min were considered as ischaemic episodes. Nocturnal arterial oxygen saturation (SaO2) was recorded perioperatively, and subjective pain was assessed every morning using a visual analogue scale (VAS).

RESULTS

Fifty-nine (OPI 30, EPI 29) patients were evaluable for efficacy. Thirteen patients (43%) in the OPI and 12 patients (41%) in the EPI group had ischaemic episodes (NS). However, significantly more patients in the OPI group had ischaemic episodes during the surgery (8 vs. 0 in the EPI group, P=0.005). The median (quartal deviation) total ischaemic burden (i.e. integral of ST-change vs. time) in patients with ischaemic episodes was ten times larger in the OPI group (340 [342] mm x min) compared with the EPI group (30 [36] mm x min) (P=0.002). There were no significant differences between the groups in average heart rates or in heart rates at the start of ischaemic episodes or in maximal heart rates during the attacks. Average nocturnal SaO2 was similar in the two groups and there were no differences in the number of hypoxaemic (SaO2<90%) episodes. Preoperatively there were no differences in subjective pain, but postoperative and average perioperative VAS scores for pain were almost 40% lower in the EPI group (P=0.006). Perioperative myocardial infarctions were not detected.

CONCLUSIONS

Continuous epidural bupivacaine/fentanyl analgesic regimen, started preoperatively, reduces the amount of myocardial ischaemia in elderly patients with hip fracture.

Correlation properties and complexity of perioperative RR-interval dynamics in coronary artery bypass surgery patients

BACKGROUND

Dynamic measures of heart rate variability (HRV) may uncover abnormalities that are not easily detectable with traditional time and frequency domain measures. The purpose of this study was to characterize changes in RR-interval dynamics in the immediate postoperative phase of coronary artery bypass graft (CABG) surgery using traditional and selected newer dynamic measures of HRV.

METHODS

Continuous 24-h electrocardiograph recordings were performed in 40 elective CABG surgery patients up to 72 h postoperatively. In one half of the patients, Holter recordings were initiated 12-40 h before the surgery. Time and frequency domain measures of HRV were assessed. The dynamic measures included a quantitative and visual analysis of Poincaré plots, measurement of short- and intermediate-term fractal-like scaling exponents (alpha1 and alpha2), the slope (beta) of the power-law regression line of RR-interval dynamics, and approximate entropy.

RESULTS

The SD of RR intervals (P < 0.001) and the ultra-low-, very-low-, low-, and high-frequency power (P < 0.01, P < 0.001, P < 0.001, P < 0.01, respectively) measures in the first postoperative 24 h decreased from the preoperative values. Analysis of Poincaré plots revealed increased randomness in beat-to-beat heart rate behavior demonstrated by an increase in the ratio between short-term and long-term HRV (P < 0.001) after CABG. Average scaling exponent alpha1 of the 3 postoperative days decreased significantly after CABG (from 1.22 +/- 0.15 to 0.85 +/- 0.20, P < 0.001), indicating increased randomness of short-term heart rate dynamics (i.e., loss of fractal-like heart rate dynamics). Reduced scaling exponent alpha1 of the first postoperative 24 h was the best HRV measure in differentiating between the patients that had normal (</= 48 h, n = 33) or prolonged (> 48 h, n = 7) intensive care unit stay (0.85 +/- 0.17 vs. 0.68 +/- 0.18; P < 0.05). In stepwise multivariate logistic regression analysis including typical clinical predictors, alpha1 was the most significant independent predictor (P < 0.05) of long intensive care unit stay. None of the preoperative HRV measures were able to predict prolonged intensive care unit stays.

CONCLUSIONS

In the selected group of patients studied, a decrease in overall HRV was associated with altered nonlinear heart rate dynamics after CABG surgery. Current results suggest that a more random short-term heart rate behavior may be associated with a complicated clinical course. Analysis of fractal-like dynamics of heart rate may provide new perspectives in detecting abnormal cardiovascular function after CABG.

Altered complexity and correlation properties of R-R interval dynamics before the spontaneous onset of paroxysmal atrial fibrillation

BACKGROUND

Trigger mechanisms for the onset of paroxysmal atrial fibrillation (AF) in patients without structural heart disease are not well established. New analysis methods of heart rate (HR) variability based on nonlinear system theory may reveal features and abnormalities in R-R interval behavior that are not detectable by traditional analysis methods. The purpose of this study was to reveal possible alterations in the dynamics of R-R intervals before the spontaneous onset of paroxysmal AF.

METHODS AND RESULTS

Traditional time and frequency domain HR variability indices, along with the short-term scaling exponent alpha(1) and approximate entropy (ApEn), were analyzed in 20-minute intervals before 92 episodes of spontaneous, paroxysmal AF in 22 patients without structural heart disease. Traditional HR variability measures showed no significant changes before the onset of AF. A progressive decrease occurred both in ApEn (1.09+/-0.26 120 to 100 minutes before AF; 0.88+/-0.24 20 to 0 minutes before AF; P<0.001) and in alpha(1) (1.01+/-0.28 120 to 100 minutes before AF, 0.89+/-0.28 20 to 0 minutes before AF; P<0.05) before the AF episodes. Both ApEn (0. 89+/-0.27 versus 1.02+/-0.30; P<0.05) and alpha(1) (0.91+/-0.28 versus 1.27+/-0.21; P<0.001) were also lower before the onset of AF compared with values obtained from matched healthy control subjects.

CONCLUSIONS

A decrease in the complexity of R-R intervals and altered fractal properties in short-term R-R interval dynamics precede the spontaneous onset of AF in patients with no structural heart disease. Further studies are needed to determine the physiological correlates of these new, nonlinear HR variability measures.

Effect of sotalol on RR interval variability during induced ventricular tachycardia

The effect of sotalol on the rate and the RR interval variability of induced ventricular tachycardia was studied in 26 patients. Sotalol increased the mean cycle length and irregularity of RR intervals, which may affect detection of ventricular tachycardia by implantable cardioverter-defibrillator devices.

Temperature-controlled slow pathway ablation for treatment of atrioventricular nodal reentrant tachycardia using a combined anatomical and electrogram guided strategy

AIMS

Anatomical and electrogram-guided techniques have been used separately for slow pathway ablation in atrioventricular nodal reentrant tachycardia. The aims of the present study were to analyse electrogram characteristics of target sites and biophysical parameters using a combined anatomical and electrogram-guided technique for temperature-controlled radiofrequency catheter ablation of the slow pathway.

METHODS AND RESULTS

Using a temperature-controlled (pre-selected 60 degrees C) catheter system, 53 patients with atrioventricular nodal reentrant tachycardia underwent slow pathway radiofrequency ablation. Mapping was started posteroseptally near the coronary sinus ostium and continued towards the midseptal area if needed. The longest and latest atrial electrograms with an atrioventricular ratio of < or = 0.5 were targeted. After a median of two pulses (mean 2.36 +/- 1.33), atrioventricular nodal reentrant tachycardia was rendered non-inducible in all patients without complications. Successful sites had longer atrial electrograms (78.8 +/- 9.8 vs 67.6 +/- 13.3 ms, P < 0.003) and larger ventricular electrogram amplitudes (92.4 +/- 51.2 vs 63.1 +/- 28.8 mV, P < 0.05) than the failed sites, but had a similar atrioventricular ratio, P-A interval and atrial electrogram amplitude. Overall, an atrial electrogram duration of > or = 70 ms was associated with effective radiofrequency delivery, with 86% sensitivity and 62% specificity. The achieved temperature maximum was 62.3 +/- 9.8 degrees C at successful and 58.8 +/- 9.0 degrees C at unsuccessful sites (ns). There was no significant difference between successful and unsuccessful applications with respect to power output, impedance and total delivery energy. During a pre-discharge study, three patients with inducible atrioventricular nodal reentrant tachycardia underwent a repeat ablation. During 12.3 +/- 2.5 (6-15) months of follow-up, three others had a clinical recurrence of atrioventricular nodal reentrant tachycardia.

CONCLUSIONS

The combined approach for slow pathway ablation is highly effective, requiring a low number of radiofrequency pulses. Long atrial activation time seems to be the most powerful predictor of success. Similar catheter tip temperature levels during successful and unsuccessful radiofrequency applications indicate that suboptimal selection of target sites rather than ineffective heating due to poor catheter tissue coupling is responsible for unsuccessful energy delivery.

RR interval variability in irregular monomorphic ventricular tachycardia and atrial fibrillation

BACKGROUND

Algorithms to reject irregular tachyarrhythmias are available in implantable cardioverter-defibrillator devices to discriminate ventricular tachycardia (VT) from atrial fibrillation (AF). The hazard of underdetection of irregular monomorphic VTs using these algorithms has not yet been fully evaluated. The purpose of this study was to determine the ability of a commonly used stability algorithm to reject AF and to correctly detect VT with a high RR interval variability.

METHODS AND RESULTS

The electrophysiological studies from 232 patients with induced monomorphic VT (cycle length > 250 ms) and 21 with AF were reviewed. A preliminary analysis was performed to classify the VT episodes in irregular (successive RR differences > 20 ms after 4 seconds from onset) or regular (otherwise). Three study groups were defined: group 1 (27 patients with irregular VT), group 2 (22 randomly selected patients with regular VT), and group 3 (21 patients with AF). A computer program analyzed the first 50 RR intervals of the induced VT (AF), resetting a VT counter if the interval was greater than a tachycardia detection interval (TDI) or if its absolute difference with the preceding three beats exceeded a programmed stability value (STAB). The VT was detected when the VT counter reached a preset number of intervals (NIDs). Different combinations of TDI, STAB, and NID were analyzed. All VTs in group 2 were correctly detected. In contrast, up to 10 VTs from group 1 were not detected when high NIDs and low STAB parameters were programmed. With usual values (10 to 16 beats and 50 to 60 ms, respectively), only 1 to 2 VTs remained undetected, but 20% to 50% had a detection delay > 8 seconds. Undetected VTs were significantly slower than early detected VTs for most STAB and NID combinations. With usual stability and NID values, 10% to 20% of episodes of AF were inappropriately detected. Changes in TDI had a small impact on sensitivity and specificity when currently used values for stability were programmed.

CONCLUSIONS

Animplantable cardioverter-defibrillator tachycardia detection algorithm with a stability criterion of 50 to 60 ms and 12 to 14 RR intervals is able to detect over 90% of monomorphic irregular VTs. Nevertheless, significant VT detection delays may arise, and inappropriate detection of AF cannot be totally prevented.

Dispersion of QT interval in patients with and without susceptibility to ventricular tachyarrhythmias after previous myocardial infarction

OBJECTIVES

The aim of this study was to estimate the value of QT dispersion measurement from the standard 12-lead electrocardiogram (ECG) in identifying patients susceptible to reentrant ventricular tachyarrhythmias after a previous myocardial infarction.

BACKGROUND

Variability in QT interval duration on the different leads of the 12-lead ECG has been proposed as an indicator of risk for ventricular arrhythmias in different clinical settings, but the value of QT dispersion measurement in identifying patients at risk for reentrant ventricular tachyarrhythmias after myocardial infarction is not known.

METHODS

The QT interval duration, QT dispersion and clinical and angiographic variables were compared between 30 healthy subjects; 40 patients with a previous myocardial infarction but no history of arrhythmic events or inducible ventricular tachycardia during programmed electrical stimulation; and 30 postinfarction patients with a history of cardiac arrest (n = 12) or sustained ventricular tachycardia (n = 18) and inducible, sustained monomorphic ventricular tachycardia by electrical stimulation.

RESULTS

Dispersion of the corrected QT interval (QTc) differed significantly between the study groups and was significantly increased in patients with susceptibility to ventricular tachyarrhythmias ([mean +/- SD] 104 +/- 41 ms) compared with that in both healthy subjects (38 +/- 14 ms, p < 0.001) and postinfarction patients with no susceptibility to arrhythmias (65 +/- 31 ms, p < 0.001). Maximal QT interval duration was also prolonged in the group with arrhythmias compared with that in the other groups (p < 0.001). Multivariate analysis, including clinical and angiographic variables, QT dispersion and maximal QT interval, showed that QT dispersion was the independent factor that most effectively identified the patient groups with and without susceptibility to ventricular tachyarrhythmias (p < 0.001).

CONCLUSIONS

Increased QT dispersion is related to susceptibility to reentrant ventricular tachyarrhythmias, independent of degree of left ventricular dysfunction or clinical characteristics of the patient, suggesting that the simple, noninvasive measurement of this interval from a standard 12-lead ECG makes a significant contribution to identifying patients at risk for life-threatening arrhythmias after a previous myocardial infarction.

Diurnal fluctuations in human ventricular and atrial refractoriness

The relative significance of the direct and indirect effects of autonomic tone on diurnal fluctuations in human ventricular and atrial refractoriness are not well known. In this study, the circadian rhythms of ventricular and atrial effective refractory periods (ERPs) were measured by noninvasive programmed stimulation in ten patients (mean age 62 +/- 10 years) who had a permanent dual chamber pacemaker for complete atrioventricular (AV) block. The ERP was measured at 4-hour intervals during spontaneous sinus rhythm with ventricular pacing (day 1) and during constant-rate dual chamber pacing (day 2). Cosinor analysis showed the ventricular ERP to have a significant diurnal rhythm in sinus rhythm (amplitude, 12 msec; 95% confidence intervals 1-24 msec) but not during constant-rate pacing (amplitude, 4 msec; 95% confidence intervals -3-12 msec). The atrial ERP had a significant rhythm at times of both spontaneous sinus rate (amplitude, 19 msec; confidence intervals 13-24 msec) and constant heart rate (amplitude, 11 msec; confidence intervals 1-21 msec) with acrophase during the sleeping hours. The increase in heart rate during dual chamber pacing resulted in a more marked decrease in the average 24-hour ERP in the ventricle than in the atrium (46 +/- 9 msec vs 12 +/- 6 msec, P < 0.01). Thus, refractoriness is more rate dependent in the ventricle than in the atrium, and autonomic influences on ventricular refractoriness are mainly indirect, via fluctuations in the sinus rate, but atrial refractoriness is also affected by direct neural influences and/or other rate independent factors.

Impaired low-frequency oscillations of heart rate in patients with prior acute myocardial infarction and life-threatening arrhythmias

Myocardial infarction results in abnormal cardiac autonomic function, which carries an increased risk of cardiac mortality, but it is not well known whether autonomic dysfunction itself predisposes patients to life-threatening arrhythmias or whether it merely reflects the severity of underlying ischemic heart disease. To determine the significance of abnormalities of cardiovascular neural regulation on the risk for ventricular tachycardia (VT), heart rate (HR) variability in the time and frequency domain were compared in a case-control study between 30 patients with a prior myocardial infarction and a history of sustained VT (n = 18) or cardiac arrest (n = 12) (VT group) and 30 patients with a prior myocardial infarction but no arrhythmic events (control group). The patient groups were carefully matched with respect to age, sex, location, ejection fraction, number of prior infarctions, number of diseased coronary arteries, and beta-blocking medication. In all patients in the VT group, inducibility into sustained VT was achieved, but none of the control patients had inducible nonsustained or sustained VT during programmed electrical stimulation. Patients in the VT group had a significantly lower SD of the RR intervals (p < 0.01), and reduced ultra low-, very low-, and low-frequency power spectral components of HR variability (p < 0.001 for all) than controls, but the high-frequency component of HR variability did not differ significantly between groups. In multiple regression analysis, reduced very low-frequency power of HR variability was the strongest independent predictor of VT susceptibility.(ABSTRACT TRUNCATED AT 250 WORDS)

Relation between heart rate variability and spontaneous and induced ventricular arrhythmias in patients with coronary artery disease

OBJECTIVES

The aim of this study was to determine the relation between autonomic control of heart rate and the spontaneous occurrence and inducibility of ventricular arrhythmias in patients with coronary artery disease.

BACKGROUND

Low heart rate variability increases the risk of arrhythmic events. It is not known whether impaired autonomic heart rate control reflects alterations in functional factors that contribute to the initiation of spontaneous arrhythmias or whether it is the consequence of an anatomic substrate for reentrant tachyarrhythmias.

METHODS

Fifty-four patients with coronary artery disease with a history of sustained ventricular tachycardia (n = 25) or cardiac arrest (n = 29) were studied by 24-h ambulatory electrocardiographic recording and by programmed electrical stimulation. Heart rate variability was compared among the patients with and without spontaneous ventricular arrhythmias and with and without inducibility of sustained ventricular tachyarrhythmias.

RESULTS

Eight patients had a total of 21 episodes of sustained ventricular tachycardia on Holter recordings. Standard deviation of RR intervals and low frequency and very low frequency components of heart rate variability were significantly blunted in patients with sustained ventricular tachycardias compared with those without repetitive ventricular ectopic activity (p < 0.05, p < 0.01 and p < 0.05, respectively). However, no significant alterations were observed in heart rate variability before the onset of 21 episodes of sustained ventricular tachycardia. Heart rate variability did not differ between the patients with or without nonsustained episodes of ventricular tachycardia. In patients with frequent ventricular ectopic activity, low frequency and very low frequency power components were significantly blunted compared with those with infrequent ventricular ectopic activity (p < 0.01 and p < 0.001, respectively). Heart rate variability did not differ significantly between the patients with and without inducible sustained ventricular tachyarrhythmias.

CONCLUSIONS

Impaired very low and low frequency oscillation of heart rate reflects susceptibility to the spontaneous occurrence of ventricular arrhythmias but may not reflect the instantaneous triggers for life-threatening arrhythmias or a specific marker of the arrhythmic substrate for ventricular tachyarrhythmias.

Effect of preocclusion stenosis severity on heart rate reactions to coronary occlusion

Autonomic mechanisms may have an important role in the clinical presentation of acute coronary occlusion. This research was designed to evaluate the effect of preocclusion stenosis severity on the immediate autonomic heart rate (HR) responses to a subsequent acute occlusion of the coronary artery. HR and its variability in the time and frequency domains were analyzed in patients with mild to moderate (< or = 85%) (group 1, n = 19) and severe (> 85%) (group 2, n = 18) left anterior descending coronary artery stenosis immediately before and during balloon occlusion (mean 108 seconds). The ranges of nonspecific responses were determined by analyzing HR reactions in a control group (n = 13) with no ischemia during balloon inflation of a totally occluded coronary artery. An abnormal increase in HR variability and/or bradycardia as a sign of vagal activation occurred in 6 patients (32%) in group 1 and in 3 patients (17%) in group 2. A significant decrease in HR variability or tachycardia, or both, was observed in 5 patients (26%) in group 1, but in none of the patients in group 2. Compared with the control group, the balloon occlusion of mild to moderate stenosis caused abnormal HR reactions more often than did occlusion of tight stenosis (58% vs 17%, p < 0.05). Balloon occlusions in group 1 caused chest pain (p < 0.01), ST-segment changes (p < 0.001), and narrowing of pulse pressure (p < 0.05) more often than did occlusions of severe stenoses.(ABSTRACT TRUNCATED AT 250 WORDS)

Clinical and angiographic prediction of myocardial infarction and recurrence of severe angina during a five-year follow-up after coronary artery bypass grafting

In a prospective, angiographically controlled study, 339 consecutive patients were examined to evaluate the pre-, peri- and postoperative risk factors for occurrence of myocardial infarction, and recurrence of severe angina during 5 years after coronary artery bypass grafting (CABG). The incidence of myocardial infarction was 6% and the recurrence of severe angina 13%. No pre- or perioperative variable could predict the occurrence of myocardial infarction. Postoperative ejection fraction was significantly lower in patients with than without myocardial infarction (58 +/- 10% vs 50 +/- 11%; p < 0.001), and the Cox proportional-hazards method showed a low postoperative ejection fraction to be the only significant risk factor for the occurrence of myocardial infarction (p = 0.02). Patients with a recurrence of severe angina had higher blood total cholesterol concentrations (7.7 +/- 1.4 vs 7.0 +/- 1.3 mmol/liter; p < 0.05) and triglyceride levels (2.7 mmol/l +/- 1.5 vs 2.0 +/- 1.0 mmol/liter; p < 0.01) than did those without angina, and also more often had > or = 1 occluded bypass graft 3 months after CABG (p < 0.05). No other pre- or postoperative variable could predict the recurrence of angina. Both total blood cholesterol concentration and triglyceride level were significant predictors of the risk of recurrent severe angina by the Cox proportional-hazards method (p = 0.01 and 0.03, respectively). Thus, reduced ejection fraction is a risk factor for subsequent myocardial infarction, whereas blood lipid abnormalities predict the recurrence of severe angina during the 5 years after CABG.(ABSTRACT TRUNCATED AT 250 WORDS)

Frequency dependent effects of d-sotalol and amiodarone on the action potential duration of the human right ventricle

Frequency dependent effects of d-Sotalol (2.0 mg/kg IV, n = 6) and amiodarone (400 mg/day for 3 months, n = 9) were studied on the action potential duration (APD) in 14 patients who underwent electrophysiological testing. Monophasic action potentials were recorded from the right ventricle at five different steady-state paced cycle lengths (700 msec, 600 msec, 500 msec, 400 msec, and 350 msec), and during ventricular extrastimuli with coupling intervals between 300 msec and 1000 msec, before and after d-sotalol and amiodarone, respectively. D-sotalol caused a prolongation of the APD at slow steady-state stimulation rates (11 +/- 5% at cycle length of 700 msec), which became attenuated at faster cycle lengths (5 +/- 3% at cycle length of 350 msec). Prolongation of APD after amiodarone was independent of pacing rate, e.g., 12 +/- 9% at cycle length of 700 msec, and 11 +/- 6% at cycle length of 350 msec. Similar frequency dependent prolongation of the APD was observed during abrupt changes of cycle lengths after d-sotalol, whereas amiodarone caused uniform prolongation of the APD at different extrastimulus intervals. Thus, d-sotalol, a nonselective potassium channel blocker, has reverse use-dependent effects on the human ventricular APD, while amiodarone with greater potassium channel selectivity, has equal ability to prolong the ventricular APD at fast and slow heart rates.

Efficacy and safety of anticoagulant therapy started pre-operatively in preventing coronary vein graft occlusion

Oral anticoagulant therapy with warfarin commenced pre-operatively (n = 102) to prevent coronary artery vein graft occlusions was compared in terms of efficacy and safety with dipyridamole and aspirin (n = 130) in a randomized consecutive series of patients. Anticoagulant therapy was started at least 2 weeks before coronary artery bypass surgery (CABG) and antiplatelet therapy was started at least 3 days before CABG with dipyridamole followed by a combination of 250 mg aspirin once a day via a nasogastric tube 6 h after CABG. Overall, vein graft patency at 3 months after surgery did not differ significantly between the anticoagulant group (203/275, 74%) and dipyridamole-aspirin group (238/311, 77%), but the occlusion rate for grafts with endarterectomy was higher in the anticoagulant (46%) than in the dipyridamole and aspirin group (16%), (P less than 0.05). The rate of peri-operative complications including deaths, re-operation and myocardial infarction was higher in the anticoagulant than antiplatelet group (26.5% vs 13.8%, P less than 0.05). The occurrence of postoperative bleeding complications did not differ significantly between the groups. Thus, oral anticoagulant therapy commenced pre-operatively has no advantages over conventional antiplatelet therapy in patients who undergo CABG. Neither antithrombotic regimens proved to be satisfactory for preventing acute bypass vein graft occlusions in this patient population with advanced coronary artery disease.

Usefulness of a postoperative exercise test for predicting cardiac events after coronary artery bypass grafting

The predictive value of a postoperative exercise test in terms of cardiac events after coronary artery bypass grafting (CABG) was prospectively studied in 231 consecutive patients. During a 5-year follow-up there were 28 cardiac events (12%), of which 15 were cardiac deaths (13 sudden), and 13 were nonfatal myocardial infarctions. There was no difference in the rate of graft patency between groups with and without cardiac events, but ejection fraction was lower in patients with than without events (51 +/- 16% vs 58 +/- 10%; p less than 0.05). Duration of the exercise test was shorter, and maximal work load was lower in patients with cardiac events (p less than 0.05 for both). The prevalence of greater than or equal to 1 mm ST-segment depression was 22% (symptomatic in 25%, and silent in 75%) and did not differ between groups with and without cardiac events. After adjustment for prognostic variables using the proportional hazards method, diuretic treatment (p = 0.007) and a low postoperative ejection fraction (p = 0.04) remained significant for predicting the risk of cardiac events within 5 years of CABG, but exercise duration and work load did not have any significant predictive value. Thus, the predictive value of a postoperative exercise test is limited, and signs of impaired left ventricular function are of greater significance for the 5-year prognosis after CABG than are those of myocardial ischemia.

Clinical and angiographic prediction of cardiac death after coronary artery bypass graft surgery

OBJECTIVES

To study the risk factors for cardiac mortality after coronary artery bypass graft surgery.

DESIGN AND SETTING

Follow up study of patients who had undergone coronary artery bypass graft surgery at the University Hospital of Oulu, Finland.

PATIENTS AND INTERVENTIONS

339 consecutive patients who underwent cardiac catheterisation three months after bypass surgery.

MAIN OUTCOME MEASURES

Incidence of cardiac deaths during the follow up period of five years and predictive value of clinical and angiographic variables for subsequent cardiac mortality.

RESULTS

The incidence of cardiac deaths was 5.1%, and 81% of these were sudden deaths. The postoperative ejection fraction was significantly lower in the patients with subsequent cardiac death than in the survivors (p less than 0.001), and their left ventricular end systolic and end diastolic volumes were higher (p less than 0.001 and p less than 0.05 respectively). The incidence of cardiac deaths was 43% in the patients with a postoperative ejection fraction of less than 40%. The myocardial jeopardy index after surgery and the rate of graft patency were not significantly different in the survivors and patients who died. The only clinical factors that were different between the groups were postoperative use of diuretics (p less than 0.001) or digitalis (p = 0.02). After adjustment for other prognostic variables by the proportional hazards method, a low postoperative ejection fraction remained significant as a predictor of the relative risk of cardiac mortality five years after operation (p less than 0.01).

CONCLUSIONS

Patients with angiographic evidence of impaired left ventricular function after bypass surgery are still at relatively high risk of dying suddenly, but myocardial ischaemia due to incomplete revascularisation is not strongly associated with an increased risk of cardiac mortality. Conventional clinical methods do not seem to be helpful for identifying patients with an increased risk of cardiac death after bypass surgery.

Prevalence and prognostic significance of exercise-induced ventricular arrhythmias after coronary artery bypass grafting

Exercise-induced ventricular arrhythmias occur often after coronary artery bypass grafting (CABG), but their prognostic significance is unknown. Two hundred patients examined by exercise electrocardiography and cardiac catheterization (including left ventriculography, bypass graft and native coronary artery angiography) before and 3 months after CABG were prospectively followed up. Exercise-induced ventricular arrhythmias occurred more often after (49 of 200 patients, 24.5%) than before (32 of 200 patients, 16.0%) CABG (p less than 0.05). There were no differences between the patients with and without ventricular arrhythmias in the prevalence of graft patency (79 vs 80%) or the postoperative ejection fraction (57 +/- 9 vs 57 +/- 12%). Ten cardiac deaths occurred during the mean follow-up time of 61 +/- 19 months, 8 of which were witnessed sudden cardiac deaths. All cardiac deaths occurred in patients who did not have exercise-induced ventricular arrhythmias after CABG. The postoperative ejection fraction was lower in the cardiac death patients (42 +/- 16%) than in the survivors (58 +/- 10%) (p less than 0.01). No other clinical or angiographic variable predicted the occurrence of cardiac death. Thus, the prevalence of exercise-induced ventricular arrhythmias increases after CABG, but the occurrence of ventricular arrhythmias does not indicate an increased risk of cardiac death.

Prevalence and prognostic significance of complex ventricular arrhythmias after coronary arterial bypass graft surgery

To assess the prevalence and long-term prognostic significance of complex ventricular arrhythmias after coronary arterial bypass graft surgery, 126 patients were studied by 24-hour ambulatory electrocardiographic recordings and cardiac catheterizations (including left ventricular, coronary arterial and bypass graft angiograms) before and 3 months after surgery, and then prospectively followed-up for a mean of 50 months. Complex ventricular arrhythmias (ventricular premature complexes greater than 30/hour, multiform and/or repetitive complexes) occurred more commonly after than before surgery (in 49/126 vs. 30/126 patients, P less than 0.05). In 18 patients (14%) who had significant worsening of ventricular arrhythmias, the ejection fraction decreased significantly (from 56 +/- 13% to 50 +/- 15%, P less than 0.05) after operation. During the period of follow-up, there were 4 witnessed sudden cardiac deaths. Complex ventricular arrhythmias tended to be more prevalent in patients who died suddenly (in 100%) compared to survivors (in 37%), but their presence did not predict the subsequent sudden death when ejection fraction was included in the stepwise regression model. None of the patients with an ejection fraction over 40% suffered sudden death despite the prevalence of complex arrhythmias in 32% of these patients. Thus, complex ventricular arrhythmias tend to occur more frequently after than before bypass surgery and their occurrence appears to be related to impairment of left ventricular function. Patients with well preserved ventricular function are at low risk of dying suddenly despite presence of complex ventricular arrhythmias after surgery.