First Commandment: Save the Brain (JACC in a Flash)
In patients with atrial fibrillation, preventing stroke, the condition's most dreaded complication, is key; more subtle neurologic consequences of AF, such as cognitive impairment and silent cerebral infarct (SCI), though, are more understated and often overlooked in the management of AF. A pair of studies appearing in a recent issue of JACC examined the cognitive impacts of ablation for AF as well as the importance of detecting AF in diabetic patients, who are particularly susceptible to the neurologic consequences of AF.
Risks of RadioFrequency Ablation
Ablation has proven to be a highly effective treatment for AF, producing a lower risk of death and dementia; however, the procedure itself carries an increased risk for transient ischemic attack and stroke. In their study, Caroline Medi, BMed, PhD, and colleagues examined the prevalence of subtle neurocognitive dysfunction following radiofrequency ablation (i.e., post-operative cognitive decline [POCD]).
Their study included 150 patients undergoing ablation—60 with paroxysmal AF (PAF), 30 with persistent AF (PeAF), and 30 with supraventricular tachycardia (SVT)—and an age-matched, nonprocedural cohort. All patients were administered a series of eight neuropsychological exams at baseline and 2 days and 3 months post-procedure (the nonoperative control group completed exams at the same time points).
In an analysis of the three procedural groups taken together, 29 patients (24%) manifested POCD at day 2 and 15 patients (13%) manifested POCD at day 90. Medi et al. conducted analyses of several cardiovascular and procedural risk factors to identify the associations between development of POCD and other variables, finding that only longer left atrial access time was significantly associated with POCD.
The etiology of POCD is likely multifactorial, the authors concluded, owing possibly to the anesthesia used, patient susceptibility, and the surgical procedure itself. The reversible impact of anesthesia, for instance, may explain why cognitive dysfunction was more pronounced at day 2 than day 90. However, AF patients experienced higher rates of late post-procedural cognitive impairment, which is more likely to directly reflect any intraprocedural cerebral insult, the authors wrote. "The long-term cognitive implications will be an important determinant of procedural safety," they added. "Furthermore, strategies to reduce the left atrial access time, optimize anticoagulation approach, and address timing of direct current reversion may have an impact on the incidence of POCD."
Silent AF and Cerebral Infarct in Diabetic Patients
Subclinical episodes of AF are believed to be a common factor in the relatively high rate of strokes of unknown cause in diabetic patients, but whether these episodes are associated with an increased risk of SCI, a more obscure neurologic complication of AF, is unknown. Raffaele Marfella, MD, PhD, and colleagues explored this question in a longitudinal, observational study of 464 type 2 diabetes patients (aged 60 and under) and 240 matched healthy subjects. All participants underwent 48-hour ECG Holter monitoring to detect brief episodes of AF.
As expected, the prevalence of subclinical AF episodes was significantly higher among the diabetic patients compared with healthy subjects (9% vs. 1.6%). According to quarterly Holter follow-up results, most of these episodes lasted 1–24 hours in the diabetic cohort, whereas only two episodes of AF (both lasting 1-24 hours) were recorded in the healthy subjects. Likewise, the mean absolute burden of AF in the diabetic group was significantly greater than the healthy group (21±15 vs. 3±1.4 hours).
Rates of stroke were higher in diabetic AF patients, who experienced a total of 43 strokes during follow-up, while no strokes were recorded in the healthy group. SCI was detected in 190 patients (41%) of the diabetic population and only 1 patient (0.5%) in the healthy population. These brief episodes of AF seemed to play a pivotal role in the risk of SCI (with an odds ratio of 4.46), independent of other cardiovascular risk factors. Additionally, longer duration of AF was associated with a higher risk of SCI. "The identification of 'brief episodes of AF' in type 2 diabetes patients may have clinical relevance in the identification of patients at risk and in the implementation of preventive measures for stroke, even after assessment of target organ damage," Dr. Marfella and colleagues concluded.
In an accompanying editorial, Eric N. Prystowsky, MD, and Benzy J. Padanilam, MD, discussed the important insights provided by these two studies, but also questioned how the current findings can influence clinical practice: "How can we reduce the harmful neurologic effects of AF in our patients? ...If the neurological sequelae of AF are not limited to stroke, have we omitted an important endpoint in the current state of AF management?" They suggest a multipronged approach, one that includes both a re-evaluation of the safety of the rate-control approach to AF and a method for better identification of patients with silent AF and significant stroke risk. "We must do more to fulfill the first commandment of therapy for patients with AF—preserve the brain."
Marfella R, Sasso FC, Siniscalchi M, et al. J Am Coll Cardiol. 2013 May 15. [Epub ahead of print]
Medi C, Evered L, Silbert B, et al. J Am Coll Cardiol. 2013 May 15. [Epub ahead of print]
Prystowsky EN, Padanilam BJ. J Am Coll Cardiol. 2013 May 15. [Epub ahead of print]
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