Atrial fibrillation and stroke: elucidating a newly discovered risk factor

What are the Risk Factors for Cerebrovascular Accidents After Elective Orthopaedic Surgery?

BACKGROUND

Perioperative cerebrovascular accidents (CVAs) are one of the leading causes of patient morbidity, mortality, and medical costs. However, little is known regarding the rates of these events and risk factors for CVA after elective orthopaedic surgery.

QUESTIONS/PURPOSES

Our goals were to (1) establish the national, baseline proportion of patients experiencing a 30-day CVA and the timing of CVA; and (2) determine independent risk factors for 30-day CVA rates after common elective orthopaedic procedures.

METHODS

Patients undergoing elective TKA, THA, posterior or posterolateral lumbar fusion, anterior cervical discectomy and fusion, and total shoulder arthroplasty, from 2006 to 2012, were identified from the American College of Surgeons National Surgical Quality Improvement Program(®) database. A total of 42,150 patients met inclusion criteria. Thirty-day CVA rates were recorded for each procedure, and patients were assessed for characteristics associated with CVA through univariate analysis. Multivariate regression models were created to identify independent risk factors for CVA.

RESULTS

A total of 55 (0.13%) patients experienced a CVA within 30 days of the procedure, occurring a median of 2 days after surgery (range, 1-30 days) with 0.08% of patients experiencing a CVA after TKA, 0.15% after THA, 0.00% after single-level anterior cervical discectomy and fusion, 0.38% after multilevel anterior cervical discectomy and fusions, 0.20% after single-level posterior or posterolateral lumbar fusion, 0.70% after multilevel posterior or posterolateral lumbar fusion, and 0.22% after total shoulder arthroplasty. Independent risk factors for CVA included age of 75 years or older (odds ratio [OR], 2.50; 95% CI, 1.44-4.35; p = 0.001), insulin-dependent diabetes mellitus (OR, 3.08; CI, 1.47-6.45; p = 0.003), hypertension (OR, 2.71; CI, 1.19-6.13; p = 0.017), history of transient ischemic attack (OR, 2.83; CI, 1.24-6.45; p = 0.013), dyspnea (OR, 2.51; CI, 1.30-4.86; p = 0.006), chronic obstructive pulmonary disease (OR, 2.33; CI, 1.06-5.13; p = 0.036), and operative time of 180 minutes or greater (OR, 3.25; CI 1.60-6.60; p = 0.001).

CONCLUSIONS

Numerous nonmodifiable patient comorbidities and increased operative time were associated with CVA after elective orthopaedic procedures. However, the American College of Surgeons National Surgical Quality Improvement Program(®) database does not code for cardiac arrhythmia or atrial fibrillation, which other studies have suggested may be important predictor variables; those may be important risk factors, although we were unable to evaluate them in our study. Surgeons should counsel patients with these risk factors and limit their operative time to reduce the risk of these adverse events, and future studies should examine other patient characteristics such as arrhythmia and noncoronary heart disease and assess the role of pharmacologic prophylaxis in patients with these risk factors.

LEVEL OF EVIDENCE

Level III, prognostic study.

Epicardially Based Pulmonary Vein Isolation for the Treatment of Atrial Fibrillation Utilizing Laser Energy in the Pig Model

Purpose: Atrial fibrillation is a common disease that increases the incidence of cerebrovascular embolic events and cardiac dysfunction. Foci for atrial fibrillation have been mapped and found to be for the most part located within the ostia of the pulmonary veins. Since 2002 microwave and radiofrequency energy sources have been used to create pulmonary vein isolation lesions. This abstract summarizes the safety and efficacy of performing vein isolation lesions with laser as the energy source. Description: The large pig model was utilized for creation of isolation lesions around the pulmonary veins. The Optimaze E360 Surgical Ablation Handpiece from Edwards Lifesciences was utilized, it contains a 4 centimeter diffusing diode laser (980nm). All six of the pig models tolerated the procedure with a 40-day normal post procedure growth pattern. Evaluation: Upon reoperation one pig developed ventricular fibrillation with resection of adhesions. All five remaining pigs were fully tested and demonstrated complete electrical isolation. Gross pathology revealed intact well defined ablation lesions with an otherwise completely normal cardiac structure. All lesions were fully transmural at each histological sectioned point. Conclusions: Laser technology in the form of the Optimaze E360 Surgical Ablation Handpiece from Edwards Lifesciences, is able to reliably and consistently produce well defined electrical isolation scars around the pulmonary veins. This device is also amenable to performing the isolation procedure using a minimally invasive approach.

Beating-heart surgical treatment of atrial fibrillation with microwave ablation

BACKGROUND

In this feasibility study, early results are presented of our first series of patients with microwave ablation for atrial fibrillation (AF) on the beating heart.

METHODS

From June 2001 until December 2001, a total of 24 patients underwent beating-heart epicardial ablation for AF. With a microwave antenna, the left and right pulmonary veins were isolated and connected to each other followed by amputation of the left atrial appendage. Subsequently, patients underwent either off-pump coronary artery bypass graft or valve surgery on pump. The mean age of the patients was 67.4 +/- 6 years. Three patients experienced paroxysmal atrial fibrillation and all others chronic AF. Mean left atrial diameter was 5.4 +/- 0.6 cm, and mean ablation time was 13 min.

RESULTS

All procedures but one were completed successfully on the beating heart. All patients were in sinus rhythm after the procedure. A total of 15 patients experienced periods with postoperative AF during hospital stay; 9 of these patients were discharged with AF. All patients received either sotalol or amiodarone. At latest follow-up (3 to 9 months), 20 of 23 patients were in sinus rhythm.

CONCLUSIONS

With microwave ablation, electrical isolation of the pulmonary veins can be achieved epicardially without cardiopulmonary bypass support.

Circadian rhythm of atrioventricular conduction predicts long-term survival in patients with chronic atrial fibrillation

The R-R interval of the electrocardiogram during atrial fibrillation (AF) appears absolutely irregular. However, the Poincaré plot of the R-R interval reveals a sector shape of distribution that is unique to AF. Furthermore, the height of lower envelope (LE1.0) of the distribution and the degree of scatter above the envelope (scattering index) may reflect the refractoriness and concealment of atrioventricular (AV) conduction, respectively. We previously observed that both the LE1.0 and scattering index show clear circadian rhythms in patients with chronic AF and that the rhythms are blunted in those with congestive heart failure and chronic AF. In the present study, we examined if the blunted circadian rhythm of the AV conduction has prognostic value in patients with chronic AF. We studied a retrospective cohort of 120 patients who underwent 24h Holter monitoring at baseline. During an observation period of 33 +/- 16 mon, there were 25 deaths (21%) including 13 cardiac and 8 stroke deaths. All patients showed significant circadian rhythms in both LE1.0 and scattering index with acrophases occurring at night; however, patients dying subsequently from cardiac causes, but not those from fatal stroke were blunted in the circadian rhythms (the amplitudes were < 55% of those in surviving patients). Furthermore, the reduced circadian amplitude of scattering index was an increased risk for cardiac death even after adjustment of coexisting cardiovascular risks [adjusted relative risk (95% confidence interval) per 1-SD decrement, 4.24 (1.54-11.6)]. When patients were divided by the circadian amplitude of the scattering index of 36.5 msec (mean minus 1-SD), the 5yr cardiac mortality below and above the cutoff was 57 and 6%, respectively (log-rank test, p < 0.001). We conclude that the blunted circadian rhythm of AV conduction is an independent risk for cardiac death in patients with chronic AF.

Reduced ventricular response irregularity is associated with increased mortality in patients with chronic atrial fibrillation

BACKGROUND-Variations in the ventricular response interval (VRI) during atrial fibrillation (AF) may be reduced in patients with adverse clinical outcomes. The properties of VRI dynamics associated with prognosis remain undetermined. METHODS AND RESULTS-In 107 patients with chronic AF (age, 64+/-9 years), we analyzed a 24-hour ambulatory ECG for VRI variability (SD, SD of successive differences, and SD of 5-minute averages) and VRI irregularity (Shannon entropy of histogram, symbolic dynamics, and approximate entropy of beat-to-beat and minute-to-minute fluctuations [ApEn(b-b) and ApEn(m-m)]). During a follow-up period of 33+/-16 months, 18 patients died (17%), 9 from cardiac causes, 7 from fatal strokes, and 2 from malignancies. Reductions in all VRI variability and irregularity measures were associated with an increased risk for cardiac death but not for fatal stroke. A significant association with cardiac death was also found for ejection fraction (relative risk, 1.10; 95% confidence interval [CI], 1.04 to 1.17, per 1% decrement) and ischemic AF (relative risk, 6.52; 95% CI, 1.62 to 26. 3). After adjustment for these clinical variables, all irregularity measures except symbolic dynamics had predictive value (relative risks [95% CIs] per 1SD decrement: Shannon entropy of histogram, 2. 03 [1.14 to 3.61]; ApEn(b-b), 1.72 [1.14 to 2.60]; and ApEn(m-m), 1. 90 [1.03 to 3.52]); however, the predictive power of variability measures was no longer significant. When the patients were stratified with the 33rd and 67th percentile values of ApEn(b-b) (1. 83 and 1.94, respectively), the 5-year cardiac mortality rates for the upper, middle, and lower tertiles were 0%, 13%, and 43%, respectively (log-rank test, P=0.04). CONCLUSIONS-Reduced VRI irregularity in a 24-hour ambulatory ECG has an independent prognostic value for cardiac mortality during long-term follow-up in patients with chronic AF.