Arrhythmias following cardiac valve replacement

Characteristics and outcomes of ventricular tachycardia and premature ventricular contractions ablation in patients with prior mitral valve surgery

BACKGROUND

Data regarding ventricular tachycardia (VT) or premature ventricular complex (PVC) ablation following mitral valve surgery (MVS) is limited. Catheter ablation (CA) can be challenging given perivalvular substrate in the setting of mitral annuloplasty or prosthetic valves.

OBJECTIVE

To investigate the characteristics, safety, and outcomes of radiofrequency CA in patients with prior MVS and ventricular arrhythmias (VA).

METHODS

We identified consecutive patients with prior MVS who underwent CA for VT or PVC between January 2013 and December 2018. We investigated the mechanism of arrhythmia, ablation approach, peri-operative complications, and outcomes.

RESULTS

In our cohort, 31 patients (77% men, mean age 62.3 ± 10.8 years, left ventricular ejection fraction 39.2 ± 13.9%) with prior MVS underwent CA (16 VT; 15 PVC). Access to the left ventricle was via transseptal approach in 17 patients, and a retrograde aortic approach was used in 13 patients. A combined transseptal and retrograde aortic approach was used in one patient, and a percutaneous epicardial approach was combined with trans-septal approach in one patient. Heterogenous scar regions were present in 94% of VT patients and scar-related reentry was the dominant mechanism of VT. Forty-seven percent of PVC patients had abnormal substrate at the site targeted for ablation. Clinical VA substrates involved the peri-mitral area in six patients with VT and five patients with PVC ablation. No procedure-related complications were reported. The overall recurrence-free rate at 1-year was 72.2%; 67% in the VT group and 78% in the PVC group. No arrhythmia-related death was documented on long-term follow-up.

CONCLUSION

CA of VAs can be performed safely and effectively in patients with MVS.

Predictors of atrial fibrillation following coronary artery bypass grafting

Background:

Atrial fibrillation (AF) is a frequent and serious complication of coronary artery bypass graft (CABG) surgery.

Methods:

We undertook a retrospective review of the records of patients undergoing CABG at Imam Ali Hospital between February 1, 2003 and February 1, 2006. The patients were divided in two groups, ie, Group A (AF) and Group B (no AF). The association between the occurrence of AF following CABG and other variables was compared with respect to continuous or categorical variables by t-test and χ²-test.

Results:

Multivariate logistic regression analysis of potentially predictive factors in univariate analysis showed that opium use, type of operation, and crossclamp time were predictors of AF following CABG.

Conclusion:

This study identifies some new predictors of postoperative AF, control of which could lead to a lower incidence of AF and reduced morbidity, mortality, and resource utilization for patients undergoing cardiac surgery.

Atrial fibrillation after cardiac surgery: a major morbid event?

OBJECTIVE

The purpose of the study was to investigate the incidence, predictors, morbidity, and mortality associated with postoperative atrial fibrillation (AF) and its impact on intensive care unit (ICU) and postoperative hospital stay in patients undergoing cardiac surgery in the Department of Veterans Affairs (VA).

SUMMARY BACKGROUND DATA

Postoperative AF after open cardiac surgery is rather common. The etiology of this arrhythmia and factors responsible for its genesis are unclear, and its impact on postoperative surgical outcomes remains controversial. The purpose of this special substudy was to elucidate the incidence of postoperative AF and the factors associated with its development, as well as the impact of AF on surgical outcome.

METHODS

The study population consisted of 3855 patients who underwent open cardiac surgery between September 1993 and December 1996 at 14 VA Medical Centers. Three hundred twenty-nine additional patients were excluded because of lack of complete data or presence of AF before surgery, and 3794 (98.4%) were male with a mean age of 63.7+/-9.6 years. Operations included coronary artery bypass grafting (CABG) (3126, 81%), CABG + AVR (aortic valve replacement) (228, 5.9%), CABG + MVR (mitral valve replacement) (35, 0.9%), AVR (231, 6%), MVR (41, 1.06%), CABG + others (95, 2.46%), and others (99, 2.5%). The incidence of postoperative AF was 29.6%. Multivariate logistic regression analysis of factors found significant on univariate analysis showed the following predictors of postoperative AF: preoperative patient risk predictors: advancing age (odds ratio [OR] 1.61, 95% confidence interval [CI] 1.48-1.75, p < 0.001), chronic obstructive pulmonary disease (OR 1.37, 95% CI 1.12-1.66, p < 0.001), use of digoxin within 2 weeks before surgery (OR 1.37, 95% CI 1.10-1.70, p < 0.003), low resting pulse rate <80 (OR 1.26, 95% CI 1.06-1.51, p < 0.009), high resting systolic blood pressure >120 (OR 1.19, 95% CI 1.02-1.40, p < 0.026), intraoperative process of care predictors: cardiac venting via right superior pulmonary vein (OR 1.42, 95% CI 1.21-1.67, p < 0.0001), mitral valve repair (OR 2.86, 95% CI 1.72-4.73, p < 0.0001) and replacement (OR 2.33, 95% CI 1.55-3.55, p < 0.0001), no use of topical ice slush (OR 1.29, 95% CI 1.10-1.49, p < 0.0009), and use of inotropic agents for greater than 30 minutes after termination of cardiopulmonary bypass (OR 1.36, 95% CI 1.16-1.59, p < 0.0001). Postoperative median ICU stay (3.6 days AF vs. 2 days no AF, p < 0.001) and hospital stay (10 days AF vs. 7 days no AF, p < 0.001) were higher in AF. Morbid events, hospital mortality, and 6-month mortality were significantly higher in AF (p < 0.001): ICU readmission 13% AF vs. 3.9% no AF, perioperative myocardial infarction 7.41 % AF vs. 3.36% no AF, persistent congestive heart failure 4.57% AF vs. 1.4% no AF, reintubation 10.59% AF vs. 2.47% no AF, stroke 5.26% AF vs. 2.44% no AF, hospital mortality 5.95% AF vs. 2.95% no AF, 6-month mortality 9.36% AF vs. 4.17% no AF.

CONCLUSIONS

Atrial fibrillation after cardiac surgery occurs in approximately one third of patients and is associated with an increase in adverse events in all measurable outcomes of care and increases the use of hospital resources and, therefore, the cost of care. Strategies to reduce the incidence of AF after cardiac surgery should favorably affect surgical outcomes and reduce utilization of resources and thus lower cost of care.

Hazards of postoperative atrial arrhythmias

Between January 1, 1986, and December 31, 1991, 4,507 adult patients underwent cardiac surgical procedures requiring cardiopulmonary bypass. Of these patients, 3,983 patients who did not undergo operation for supraventricular tachycardia and who were in normal sinus rhythm preoperatively form the study group for the present study. Postoperatively, all patients were monitored continuously for the development of arrhythmias until the time of hospital discharge. The incidence of atrial arrhythmias requiring treatment for the most commonly performed operative procedures were as follows: coronary artery bypass grafting, 31.9%; coronary artery bypass grafting and mitral valve replacement, 63.6%; coronary artery bypass grafting and aortic valve replacement, 48.8%; and heart transplantation, 11.1%. For all patients considered collectively, the risk factors associated with an increased incidence of postoperative atrial arrhythmias (p < 0.05 by multivariate logistic regression) included increasing patient age, preoperative use of digoxin, history of rheumatic heart disease, chronic obstructive pulmonary disease, and increasing aortic cross-clamp time. Postoperative atrial fibrillation was associated with an increased incidence of postoperative stroke (3.3% versus 1.4%; p < 0.0005), increased length of hospitalization in the intensive care unit (5.7 versus 3.4 days; p = 0.001) and postoperative nursing ward (10.9 versus 7.5 days; p = 0.0001), increased incidence of postoperative ventricular tachycardia or fibrillation (9.2% versus 4.0%; p < 0.0005), and an increased need for placement of a permanent pacemaker (3.7% versus 1.6%; p < 0.0005). These data provide a basis for targeting specific patient subgroups for prospective, randomized trials of therapeutic modalities designed to decrease the incidence of postoperative atrial arrhythmias.

Is high potassium solution necessary for reinfusions in "multidose" cold cardioplegia? A randomized prospective study using computerized Holter system

Multidose potassium cardioplegia is a common method of myocardial preservation. Although initial potassium arrest conserves high-energy phosphates, there is conflicting evidence that repeat high potassium boluses augment this protection. Fifty-six patients were prospectively randomized to receive multidose cold high potassium cardioplegia (27 mEq of KCl/L) both in the initial and subsequent infusions (Group 1) or an initial cold high potassium (27 mEq/L) cardioplegia followed by boluses of cold low potassium (7 mEq, of KCl/L) solution (Group 2). The two groups were compared in terms of postoperative myocardial electrical stability and hemodynamic performance. Electrocardiograms were recorded by continuous Holter monitor, and the data were analyzed by computer. The duration of aortic cross-clamping and cardiopulmonary bypass did not differ between groups. Group 1, who received more total KCl than Group 2 (p less than .005), experienced more high-grade ventricular ectopia during both reperfusion (p less than .001) and the immediate postoperative period (p less than .001), and required more lidocaine hydrochloride (p less than .001) for arrhythmias. There was no significant difference in hemodynamic performance between the two groups. This study fails to show an advantage to multidose "high potassium" cardioplegia and found a significant increase in ventricular ectopia associated with its use. We advocate using low potassium solutions after initial cold high potassium arrest.

Comparison of the effectiveness of myocardial preservation in right atrium and left ventricle

Ten patients underwent cardiac operations during which myocardial preservation was provided by systemic hypothermia, topical cardiac cooling, and cold blood cardioplegia. The duration of ischemia ranged from 45 to 142 minutes (mean, 84.2 +/- 36.2 minutes). Two serial specimens (preischemic and ischemic) were obtained from the right atrium and the left ventricle, respectively; thus, a total of 40 biopsy specimens was obtained from these 10 patients. A combination of grading of ischemic injury and stereological morphometric measurement of mitochondria was performed to assess the effectiveness of myocardial preservation. Our findings from the mitochondrial score studies (grading of ischemic injury) were as follows. In the right atrium, the average mitochondrial score rose from 0.337 +/- 0.235 in the preischemic stage to 1.969 +/- 0.492 in the ischemic stage. In contrast, the average mitochondrial score for the left ventricle was only elevated from 0.380 +/- 0.161 to 1.353 +/- 0.396. The difference between preischemia of the right atrium and left ventricle is not statistically significant, but the difference between ischemia of these chambers is significant (p less than 0.01). Our stereological morphometric studies revealed that in the left ventricle, the average mitochondrial surface area was 0.316 +/- 0.046 micron 2 in the preischemic stage and 0.347 +/- 0.073 micron 2 in the ischemic stage, a 9.8% increase in mitochondrial size (not significant). In contrast, the mitochondrial surface area of the right atrium showed a mean increase of 65.8%, from 0.231 +/- 0.038 micron 2 in the preischemic stage to 0.383 +/- 0.057 micron 2 in the ischemic stage (p less than 0.001).(ABSTRACT TRUNCATED AT 250 WORDS)

Perioperative Holter monitoring and computer analysis of dysrhythmias in cardiac surgery

In order to increase the accuracy and efficiency of studying perioperative dysrhythmias, 52 patients undergoing cardiac surgery were fitted preoperatively with a Holter monitor adapted for intraoperative recording, and the preoperative, intraoperative and early postoperative cardiac electrical activities were classified with a digital computer. Forty patients underwent coronary artery bypass grafting (CABG), eight had valve replacements, and four had combined procedures. The results showed the following: (1) high incidence of various dysrhythmias occurring during anesthesia induction and thoracotomy prior to aortic cross-clamp; (2) high incidence of continued atrial activity during cardioplegia; (3) lack of correlation between peak serum CPK-MB levels and dysrhythmias; and (4) a higher overall incidence of dysrhythmias in valve patients. Adapting the Holter monitor technique for cardiac surgery can solve the problem of observer vigilance inherent to such a study using a human "monitor watcher," and facilitate the accurate analysis of the vast amount of data obtained. This is important in quantitating the electrophysiologic effects of various perioperative interventions, such as the anesthetic agents, beta-blockers, calcium antagonists, and cardioplegic solutions.

Ventricular arrhythmias before and late after aortic valve replacement

The influence of aortic valve replacement on the incidence of ventricular arrhythmias was studied by 24-hour Holter electrocardiographic monitoring in 45 patients immediately before and 14 +/- 7 months after operation. Ventricular arrhythmias were graded according to the Lown criteria. Preoperative left ventricular (LV) ejection fraction (EF) was determined by angiography and postoperative LVEF by gated blood pool scintigraphy. Repetitive ventricular arrhythmias (Lown grade 4A/B) were associated with a reduced LVEF (less than 55%) before and after operation. In 24 patients with preoperative normal LVEF (greater than or equal to 55%) (group A), mean LVEF remained unchanged after operation (72% vs 71%). Pre- and postoperative ventricular premature complex (VPC) frequency (45 +/- 99 vs 39 +/- 94 VPC/24 hours) and grade (1.3 vs 1.4) were not significantly different. However, in 17 patients with preoperative impaired LVEF (less than 55%) (group B, LVEF preoperatively 40 +/- 8%) and marked postoperative improvement (greater than 10%) (LVEF postoperatively 64 +/- 7%), mean VPC frequency decreased from 536 to 69 VPCs/24 hours and mean VPC grade was reduced from 3.8 to 1.5. Complex VPCs were found preoperatively in all 17 patients of group B, but in only 5 patients after operation. Four patients had a reduced LVEF preoperatively and it did not improve postoperatively (group C). Postoperative Holter monitoring detected ventricular tachycardia in all 4 patients. This study indicates that repetitive VPCs are infrequent in patients with normal LVEF before and late after aortic valve replacement. In patients with impaired LVEF and complex VPCs preoperatively, the postoperative improvement of LV function is usually accompanied by a reduction of frequent and complex VPCs.

Aortic valve replacement in patients with aortic stenosis. Effect on cardiac arrhythmias

Twenty-four hour ambulatory electrocardiography was performed on 28 patients with aortic stenosis without significant coronary artery disease or aortic regurgitation. Compared to a control group of subjects with normal hearts proven by noninvasive and invasive testing, patients with aortic stenosis had higher (p = 0.0001) frequency of premature ventricular contractions (PVC) (3144 +/- 1425 versus 17 +/- 46) per 24 hours and higher (p = 0.001) prevalence of PVC presence (27 of 28 patients versus 39 of 101 normal), and complexity (19 of 28 patients versus 4 of 101 normal). Weak correlations of complexity with left ventricular end-diastolic pressure (r = 0.30) and ejection fraction (r = -0.25) were noted. No correlation of ventricular ectopic activity with peak systolic gradient, aortic valve area, or peak left ventricular systolic pressure was noted. Repeat 24-hour ambulatory electrocardiography performed on 13 patients three months after successful aortic valve replacement did not show significant effect of aortic valve replacement on PVC frequency or complexity.

Postoperative supraventricular arrhythmias and the role of prophylactic digoxin in cardiac surgery

A prospective study of 182 patients undergoing cardiac surgery was performed. The patients were divided into three groups. Group I consisted of 83 patients who had never been treated with digitalis. Group II comprised 59 patients who were taking digoxin before operation and had medication discontinued 24 to 48 hours prior to surgery; they did not receive maintenance digoxin in the postoperative periods. Group III was made up of 40 patients who were given prophylactic digoxin in the perioperative period; none had taken digoxin before. Sixty of 83 group I patients (72%) and two of the group III patients (5%) developed postoperative supraventricular tachyarrhythmia. Digoxin was reinstituted in 56 of group II patients (95%) for supraventricular arrhythmia and/or heart failure. Of the various factors evaluated, only valvular surgery and ECG evidence of myocardial infarction were associated with postoperative supraventricular tachyarrhythmias.

Role of intravenous verapamil in supraventricular tachyarrhythmias after open-heart surgery

Although the antiarrhythmic effects of verapamil (V) have been studied widely, its role in the treatment of atrial tachyarrhythmias after open-heart surgery (OHS) has not been defined. Accordingly, 22 patients were studied using a double-blind randomized crossover protocol 1 to 6 days after OHS, except for one patient, who was studied 90 days after OHS. Atrial fibrillation was seen in 18 and atrial flutter was observed in four patients. Two doses were used, 0.075 and 0.15 mg/kg (not exceeding 10 mg per dose), depending on the response. A positive response consisted of: conversion to sinus rhythm or heart rate less than 100 beats/minute (bpm). Eleven patients received V as the first drug; the remaining 11 received placebo first. Digoxin had been given to 20 patients (0.5 mg average dose) prior to inclusion in the study. Four patients converted to sinus rhythm within 30 minutes after V and one additional patient did so within 10 seconds of placebo administration. The post treatment heart rate combining both low and high dose response was 85 +/- 18 compared to 128 +/- 23 bpm for placebo (M +/- SD, p less than 0.01). The heart rate remained lower than control 30 minutes after V. Transient hypotension required intravenous fluid in one patient. Thus, V safely and rapidly controls heart rate but is not likely to result in immediate conversion to sinus rhythm in patients after OHS.

Effect of sodium nitroprusside during the payback period of cardiopulmonary bypass on the incidence of postoperative arrhythmias

This study was designed to determine whether a sodium nitropruside infusion during the reperfusion (payback) period of cardiopulmonary bypass would minimize arrhythmias during the early postoperative period of coronary artery bypass surgery. A double-blind randomized study was carried out in 38 patients with no previous history of ventricular arrhythmias. Seventeen received 5% dextrose in water (D5W) and 21 received sodium nitroprusside at the rate of 2 microgram per kilogram per minute during the payback period. The pump flow was kept constant at 2.2 liters per square meter per minute, and mean pressure was maintained at greater than 50 mm Hg. There was a statistically significant difference between the two groups in the number of patients who developed ventricular arrhythmias (13 of 17, or 76%, in the D5W group versus 6 of 21, or 29%, in the sodium nitroprusside group; p less than 0.005). Twelve of the 13 patients in the D5W group experienced arrhythmias (6 ventricular tachycardia and 6 ventricular premature depolarization) within the first 24 hours, compared to 5 of 12 patients in the nitroprusside group (3 ventricular tachycardia and 2 ventricular premature depolarization). Only 1 patient in each group developed ventricular arrhythmia after the first postoperative day. One patient in each group experienced atrial arrhythmia during the first 24 hours. After 24 hours, atrial arrhythmias developed in 5 patients in the D5W group (35%) and 3 patients in the sodium nitroprusside group (17%) (p greater than 0.05). The arterial pH ranged from 7.35 to 7.55, with a Po2 greater than 70 torr and a serum potassium of 3.7 +/- 0.36 mEq per liter in the D5W group and 3.4 +/- 0.34 mEq per liter in the nitroprusside group during the period of arrhythmias. Sodium nitroprusside given during the payback period of cardiopulmonary bypass appears to minimize ventricular arrhythmias in the early postoperative period of coronary artery bypass surgery.

The role of P wave duration as a predictor of postoperative atrial arrhythmias

Atrial fibrillation (AF) and flutter (AFI) occur frequently after aortocoronary bypass grafting. To identify patients at highest risk, we observed 99 patients undergoing aortocoronary bypass surgery. P wave duration was measured on a three-channel ECG. An intra-atrial conduction defect (IACD), defined by conventional criteria as a single standard lead P wave greater than 110 msec, was present in 42 patients. We also identified IACDs by measuring the total P wave duration (TPWD) from the simultaneous three-channel recording of the standard leads (IACD-TPWD). Sustained AF-AFI, less than one hour, occurred in 29/99 patients. Of the 29 patients with AF-AF1, 24 had IACD-TPWD. The mean total P wave duration of patients with and without AF-AFI was 126 msec and 116 msec, respectively (P less than .001). The mean P wave duration measured conventionally (ECG lead 2) was 114 msec in the patients with AF/-AFI and 110 msec in patients without AF/-AFI. An isoelectric interval (IEI), derived by subtracting the ECG lead 2 P wave duration from the total P wave duration measured from three simultaneous limb leads, for patients without AF-AFI was 5.9 msec vs 12.4 msec for patients with AF-AFI (P less than 0.001). Of the patients with IACD-TPWD, 24/64 (38 percent) had AF-AFIRM; of the patients without IACD-TPWD, 5/35 (14 percent) had AF-AFI (P less than .05). The mean ages, number of bypass grafts, preoperative propranolol dose and prevalence of digoxin use presence of IACD-TPWD is a sensitive but non-specific predictor of AF-AFI after bypass surgery, and a prolonged IEI enhances the specificity.

Propranolol for prevention of postoperative cardiac arrhythmias: a randomized study

Two hundred twenty-three patients were randomly selected to receive propranolol, 10 mg orally every 6 hours, or to serve as controls after coronary artery bypass grafting. The study began at the time of discharge from the intensive care unit. Patients were ineligible if they had cardiac arrhythmias while in the intensive care unit, low cardiac output requiring catecholamine support, or bradycardia requiring a pacemaker. In the control group, cardiac arrhythmias for which treatment was necessary developed in 31 of 136 patients (23%), atrial fibrillation or flutter in 24 patients (18%), and ventricular arrhythmias in 7 (5%). In the group receiving propranolol, cardiac arrhythmias requiring treatment developed in 9 of 87 patients (10%), atrial fibrillation or flutter in 7 (8%), and ventricular arrhythmias in 2 (2%). The difference in frequency with which cardiac arrhythmias occurred between the two groups is significantly different (p less than 0.05). We conclude that propranolol is effective in the prevention of cardiac arrhythmias following coronary artery bypass grafting.

Arrhythmias and conduction disturbances following aortic valve implantation

In the first postoperative week following aortic valve implantation, arrhythmias and conduction disturbances were seen in 37 of 44 patients studied. Sixty-seven episodes of arrhythmias occurred, atrial fibrillation and accelerated junctional rhythms accounted for more than 75% of these episodes. Episodes of atrial fibrillation were most common after the age of sixty.l When atrial premature contractions were observed, episodes of atrial fibrillation followed shortly afterwards. Accelerated junctional rhythms were seen in 17 patients and affected the patients haemodynamically when this dysrhythmia occurred early in the postoperative course, but improvements were seen promptly following atrial overpacing. Lidocaine was infused prophylactically for 2 days in patients with severe aortic stenosis or marked left ventricular hypertrophy. One episode of ventricular fibrillation and few incidents of ventricular extrasystoles were seen. Most conduction disturbances were transient, but bundle branch block persisted in 3 patients, and there was complete A-V block in a fourth. No causal relationship between the use of digitoxin and the frequency of arrhythmias could be established.

Lesions of conduction tissue complicating aortic valvular replacement

A pathologic study of the cardiac conduction system was performed in 57 patients who died within 30 days after aortic valvular replacement. Histologically, there were old and recent lesions present in 34 (60 percent) and 43 (75 percent) of the patients, respectively. Old lesions did not show meaningful correlation with preoperative electrocardiograms. Although nontraumatic recent lesions were rarely the cause of postoperative abnormal cardiac conduction, traumatic lesions were frequently associated with loss of sinus mechanism. The main cause of trauma to the major cardiac conduction tissue was injury by sutures. The short membranous septum predisposed to injury, while the configuration of the left ventricular outflow tract was not a significant factor in injury. Traumatic lesions of the cardiac conduction tissue were more common in subjects with bicuspid than tricuspid aortic valves.

Arrhythmias following cardiac surgery: relation to serum digoxin levels

Arrhythmias were analyzed in 50 patients undergoing cardiac surgery: 27 with valve surgery, 15 with coronary artery bypass (CAB), 5 with CAB and valve surgery, and 3 with miscellaneous procedures. The role of electrolyte abnormalities, pericarditis, serum osmolarity, digoxin level, and the type of surgery performed was evaluated. Thirty-seven out of 50 patients (74 per cent) had a postoperative arrhythmia, and a total of 78 different arrhythmias were noted. Twenty-six out of 27 patients with valve surgery had an arrhythmia vs. six out of 15 patients with CAB (p less than 0.001). Atrial fibrillation was the most common arrhythmia in all groups. Although postoperative hypocalcemia, hypomagnesemia, pericarditis, and wide shifts in osmolarity were common, they did not correlate with arrhythmias. Seventeen patients developed postoperative arrhythmias compatible with digitalis toxicity, including junctional rhythm, atrioventricular dissociation, or atrial tachycardia with block. However, the range of serum digoxin levels in these patients was zero to 2.80 ng. per milliliter. This suggests increased sensitivity to digitalis glycosides or the effects of surgical trauma as the etiology of arrhythmia in many patients. The distinction between digitalis-induced arrhythmia and spontaneously occurring arrhythmia cannot be made with certainty in most postoperative patients. Therapy should reflect an awareness of the potential for postoperative digitoxicity.