Correct answer is implantation of a permanent pacemaker. Now, the observations are that she has a resting ECG with a left axis deviation, and this is actually in this case, been progressive. She developed a rate-related IVCD with heart rates in excess of 110 beats per minute. There are several approaches to this problem depending upon clinical circumstance and details. She actually has been significantly symptomatically improved on myxilatin in terms of her skeletal muscle disease and was really quite reluctant to come off this medication. Implantation of a pacemaker would allow her to be safely treated and continue to be safely treated with myxilatin. If anything was going to be implanted in this case, probably should be a pacemaker and not a monitoring device. Continued routine follow-up in a patient with myotonic dystrophy who's demonstrating progressive changes in conduction probably is not the best approach in this case. A bit of a consideration of myotonic dystrophy here for just a few minutes. These patients are generally fairly young. Sudden death occurs in about 15 percent. Fifteen percent sudden death rate in patients with myotonic dystrophy is actually a high sudden death rate. In fact, in this case, bradycardia may be as prominent as tachycardic causes of sudden cardiac death. Conduction block is fairly common in type 1 myotonic dystrophy and, in fact, has an unpredictable course. There is a general but not tight correlation with severity of skeletal muscle disease in terms of conduction system disease in the heart. Atrial fibrillation is actually relatively common as well at 15 percent, and about 15-20 percent patients with myotonic dystrophy will have left ventricular dilatation or systolic dysfunction. However, relatively few develop heart failure symptoms. This may be a result of early mortality and lack of time to develop heart failure symptoms, but suffice it to say, this folks generally don't. I think one of the largest studies of now over 15 years ago was an observational study of patients with what are called severe abnormalities of the ECG and myotonic dystrophy. Severe abnormalities were rhythm other than sinus like atrial fibrillation, PR interval prolongation, QRS duration prolongation, or second or third degree AB block. This was an observational study over six years. Remarkably, about 24-25 percent developed severe ECG changes. This occurred again at a relatively young age, roughly 49 years and a bit of a slight prominence in women. There were 81 deaths in this cohort of over 400 patients and the mean age of deaths was 54 years of age. Twenty-seven of those, seven percent were sudden deaths, so high incidence of death. Remarkably, heart failure itself with or without ECG changes was relatively uncommon, a little bit more common when patients had ECG changes. Again, this is a skeletal muscle disease with profound impacts on the heart and particularly those that develop in the conduction system really demand evaluation treatment. What do we do? Well, supportive care for skeletal muscle disease is important. Sodium channel blockers are useful for patients with severe myotonia, such as myxilatine, propofenone, or diphenylhydantoin. IVCDs and AV conduction block are relative contraindications here. But for example, in this patient who got a fair bit of symptomatic benefit from myxilatine, backup pacing support may be an option to allow for continued treatment with these medications. Pacing is required in these folks who have acquired AV block irrespective of the presence of symptoms related to AV block. Lower grade AV block is also an indication for pacing because of the unpredictable rate of progression of AV block. In some cases, particularly when the heart's dilated, there's a substrate for ventricular tachycardia and ventricular fibrillation. In fact, bundle branch reentrant tachycardia is observed in myotonic dystrophy in patients particularly with LV enlargement. One other thing to consider in managing these patients is that myotonia can be exaggerated in the OR or in the cath lab by depolarizing relaxants such as succinylcholine or anticholinesterases such as neostigmine. It's important to remember that barbiturates, opiates, and benzodiazepines can produce apnea and actually prolong recovery from anesthesia. Important to keep in mind in managing patients with myotonic dystrophy.

myotonic dystrophy

permanent pacemaker

cardiac conduction

sudden cardiac death

skeletal muscle disease