Neuro Critical Care

  Download article as PDF >

 

Developments in Stroke Prevention
by Brett Gidney, MD, cardiac electrophysiologist

 

One in five strokes is related to atrial fibrillation (Af) and therefore preventable with vigilance and appropriate referral (CDC data).

 

Vitamin K antagonists prevent about 64 percent of AF-related thromboemboli, whereas newer drugs like dabigatran, an oral direct thrombin inhibitor, prevent 66 percent. Recent data demonstrate that many of the 25 to 30 percent of strokes thought to be cryptogenic are actually not cryptogenic, but rather due to AF; thus, the CDC data that 20 percent of strokes are due to AF is a significant underestimate. Exciting new therapies beyond anticoagulants are available here on the Central Coast.

 

Small devices called implantable loop recorders (ILRs) are changing our perception of the prevalence of AF in the stroke population. ILRs are tiny (8cc/17gram) devices that detect AF when placed subcutaneously via a 1.5cm incision during a 15-minute procedure using only local anesthetic.

 

Brett Gidney, MD

 


See Case Report below >


 

The data an ILR records are wirelessly transmitted to an in-office programmer, and the ILR battery lasts for years. ILRs should be given to patients with cryptogenic stroke, and large studies such as TRENDS (Stroke, 2010) found that 28 percent of cryptogenic stroke patients were found to have AF. Rather than conventional treatment of cryptogenic stroke with only aspirin, these patients with AF detected after what was initially thought to be a cryptogenic stroke are suddenly candidates for highly effective treatment with oral anticoagulation therapy (OAT) i.e. Warfarin. Unfortunately, due to the dramatic effect of aging on stroke risk in AF, many of the patients identified as having high risk of first or recurrent stroke have contraindications to OAT.

 

New left atrial appendage exclusion devices are available to patients via cardiac electro-physiologists to prevent AF-related stroke without anticoagulation (obviating the need to worry about bleeding). One such device is FDA- approved and called the LARIAT. The device ties off the appendage via a technique similar to pericardiocentesis.

 

It is performed entirely within the cardiac catheterization suite without the need for surgery. The LARIAT is being used at select centers, including Santa Barbara Cottage Hospital, to permanently occlude the atrial appendage. Any patient with AF at risk for thromboembolism who is not a candidate for anticoagulation is eligible. This device results in complete appendage occlusion in 98 percent of patients. A prospective study showed that occluding the atrial appendage with a similar device reduced ischemic stroke by 75 percent (much better than anticoagulation).

 

 

 

An implantable loop recorder is placed subcutaneously

 

AF is epidemic. Once over age 40, a person's lifetime risk of AF is one in four. AF is not just a nuisance that requires rate control. Rather, this disease is interestingly nuanced. Many, if not all, patients with a cryptogenic stroke should be referred to an AF specialist to verify no underlying AF. Second, we are no longer justified in simply writing off the risk of stroke because of high bleeding risk. From the accident-prone athlete, to the motorcycle enthusiast, to the assisted-living patient with frequent falls, to the cryptogenic stroke patient otherwise consigned to lifelong aspirin therapy, strokes may be assessed using diagnostics like implantable loop recorders and prevented without anticoagulation by using the LARIAT.

 

Case Report: Treatment for Atrial Fibrillation

 

A 76-year-old female is referred for evaluation of paroxysmal AF previously controlled with propafenone. AF episodes last many hours with spontaneous resolution and symptoms that include palpitations and fatigue; the fatigue often lasts many hours following return to normal rhythm. The episodes of palpitations occur daily, often at night after a glass or two of red wine. The AF initially responded to medication with two years of scant symptoms, but crescendo breakthrough with daily episodes despite propafenone prompted referral. In the past, oral anticoagulation was withheld since the patient feared trauma-related bleeding from her daily horseback riding. In fact, she had recent pelvic trauma due to a fall off her horse.

 

After being told of high stroke risk based on her CHA2DS2-VASc score above 2, she consents to initiating Coumadin. Symptoms were the primary reason for referral, and she requests ablation to achieve symptom abatement. She understands the expected success rate is nearly 80 percent and 30 percent of patients need a second ablation for optimal outcome. The first ablation is uneventful with successful isolation of her pulmonary veins. Vagal episodes accompany radiofrequency ablation near the Coumadin ridge, the junction between the left superior vein and left atrial appendage, and particular attention is given to this vicinity as these vagal events likely indicate successful modification of the nearby left superior ganglionic plexus, an important mediator of AF.

 

Over the subsequent months, episodes of AF are much better with only several for less than an hour each despite no antiarrhythmic medication. With her goal of complete cure, she undergoes repeat ablation at three months for these continued, albeit improved, symptoms. At nine months after the second ablation off all drugs except anticoagulation she describes ongoing fear of riding horses due to bleeding risk from anticoagulation. She admits to rare palpitations in the middle of the night that are gone by morning. These episodes, if truly AF, are possibly enough to result in a cerebral vascular accident off OAT. She agrees to have a Reveal loop recorder implanted, and rare symptomatic and asymptomatic episodes of AF lasting for up to 20 minutes are seen on the device memory. Given her high CHA2DS2- VASc risk score and bleeding risk from horseback riding, she is offered the LARIAT procedure to close her left atrial appendage and eliminate OAT. A CT of her left atrium confirms that her left atrial appendage size and orientation are adequate to close the appendage. An overnight stay at Santa Barbara Cottage Hospital is planned with the expectation to permanently stop anticoagulation one week prior to the procedure.

 

< Return to Fall 2012 NEUROtransmitter >> Download PDF

 

 010213