Aggressive BP Therapy Won't Stop AF Recurrences After Ablation: SMAC-AF

Larry Hand

November 15, 2016

NEW ORLEANS, LA — Aggressive blood-pressure–lowering therapy in the months prior to scheduled ablation of atrial fibrillation (AF) did not provide sustained protection against AF recurrence 3 months after the procedure, in a randomized, open-label trial presented here at the American Heart Association (AHA) 2016 Scientific Sessions[1].

"The average number of blood-pressure medications that patients were on was three," Dr Ratika Parkash (QEII Health Sciences Center, Halifax, NS) told heartwire from Medscape.

"The effect on blood pressure was quite dramatic early on in the study. Patients achieved their target blood pressure certainly by 3 months postablation. The mean blood pressure at 6 months was 123 mm Hg across the board, and three-quarters of patients achieved a blood pressure of less than 120 mm Hg," she said.

Parkash and colleagues conducted the randomized, open-label Substrate Modification with Aggressive Blood Pressure Control (SMAC-AF) (SMAC-AF) trial involving 184 patients with hypertension randomized to either aggressive blood-pressure treatment (n=92) or standard blood-pressure treatment (n=92) up to 6 months prior to scheduled AF ablation. The final analysis involved 88 patients in the aggressive-therapy group who went on to ablation and 85 in the standard-therapy arm who went on to ablation.

Mean patient age was about 60 years, and three-quarters were men. Mean body-mass index was about 32 and mean blood pressure was 143.9/84.9 in the aggressive arm and 142.2 in the standard arm; 16.3% of the aggressive arm had diabetes, compared with 10.9% of the standard arm.

Minimum follow-up was 12 months and maximum follow-up was 30 months from randomization.

Patients in the aggressive arm experienced a decrease in blood pressure to a mean of 123.2/80.8 at 6 months, while patients in the standard group had a mean blood pressure of 135.4/76.7. Blood pressure had risen slightly in the aggressive group while the standard group experienced a slightly lower blood pressure at the time.

About a quarter of the patients in the aggressive group experienced hypotension.

For the primary outcome of time to recurrent symptomatic AF/atrial tachycardia/atrial flutter 3 months postablation, both groups had about a 60% incidence at 24 months (hazard ratio 0.94; 95% CI 0.65–1.38; P=0.73). About a quarter of all patients had an AF-related emergency-department visit, and about 10% had AF-related hospitalizations.

"Duration of therapy prior to ablation was a median of 3.5 months and may not have resulted in adequate effect," Parkash said during the presentation. "The atrial myopathy in these patients with a prolonged and high AF burden may not be reversible."

The fact that the treatment didn't hold up "is what I'm struggling with," she told heartwire . "It's possible that the length of time that we treated the patients was inadequate or that the atrial substrate was too far advanced in the population that we chose. These people were at very high risk for recurrent atrial fibrillation. They embodied every possible indicator for recurrent atrial fibrillation.

"This study raises a lot of questions for us with respect to patients who already have atrial arrhythmia and what we can do to prevent recurrence. It is different from those patients who have not yet developed atrial fibrillation," she said.

"The first thing we need to ask is, was the intervention successful?" Dr Jonathan P Piccini (Duke Clinical Research Institute, Durham, NC), discussant at the presentation, said. "And indeed we see significant blood pressure that appears to sustain throughout the study. But when we look at the outcomes, we see that there was no major difference in recurring atrial arrhythmias in follow-up.

"We need to keep in mind that there are some limitations, as there are in any clinical trial. The patients were treated only for a median of 5 months. Perhaps there was insufficient preablation study. And finally, the sample size was relatively modest," he said.

"I think it's the fact that aggressive blood-pressure control alone may be too little. Targeting a single risk factor in isolation following catheter ablation is likely suboptimal. Future efforts will most likely target multiple risk-factor interventions and optimize care of the entire patient," he concluded.

Parkash reported receiving research support from St Jude Medical and Medtronic. Disclosures for the coauthors are listed in the abstract.

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