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Blocked PAC
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Blocked PAC

Hello,
I am a 35 year old female with a history of mild aortic vlave disease, mitral valve insufficiency, papiations and I am currently being treated for hypokalemia (3.1). I do also suffer anxiety. I recently wore a event monitor for episodes of a racing heart. A week prior to wearing the monitor I was taken to the hospital for a heart rate of 160 and what the EMT said was SVT. I was giving a shot of adenosine which only brought my  heart rate back down to 123. At the emergency department doctor looked over the ecg he said I was not in SVT and it was just sinus tachycardia. The doctor believed it was do to dehydration. I went to my cardiologists for the monitor and wore it for 2 weeks the findings where sinus tachycardia, and a pauce of 2.8sec. while awake. The doctor called this a blocked pac and said it didn't reach the ventricles ,said it was normal and if I would start to pass out or it would reach a 5 sec pause I would need a pacemaker. Getting a possible pacemaker doesn't sound normal. He made it sound as if it was not a big deal. My question is this something I should worry about? I have young children and don't want to be in a car and pass out and hurt them or someone else. He did refer me to a cardiologist that specializes in heart rhythms but I will not see him for 3 months. I always seem to have tons of questions when I leave but I am going crazy having to wait that long and I can't seem to find any information on this, the olny thing I found is that it is called a nonconducted pac and that it usually happens during sleep. Could you please give me a little more information on this. And what is your prefessional opinion, is a 2.8 sec pause not a big deal?
Thanks for your time :)
4610897_tn?1393869202
Hello. Thank you for your question. I have read your case scenario and these are some of my thoughts:

A PAC is a premature atrial contraction. It is due to an ectopic (a focus of electricity in the heart other than from the usual location – the sinus node) beat that is usually “conducted” down the atrioventricular node to the ventricles via the atrioventricular node and bundle of HIS. However, sometimes, the AV node does not allow the impulse (electrical activity) to pass down it (it is “refractory” to it). This results in a blocked PAC and is the MOST COMMON and benign (not dangerous) cause of sinus pauses. Patients DO NOT get pacemakers for blocked PAC’s and blocked PAC’s DO NOT cause patients to have syncope (pass out).
I also think you should ask the cardiologist (or electrophysiologist – cardiologist with advanced training in arrhythmia (electrical disorder of heart) about the possible that the rhythm you to the ER for was not sinus tachycardia, but rather atrial tachycardia, which may have caused a racing heart. This is impossible to tell however without the original tracings from the ER. This is not necessarily a dangerous rhythm, but can be symptomatic and can be treated with medications like beta-blockers and calcium channel blockers to slow the heart. In addition, it can be “ablated” with radiofrequency waves by electrophysiologists. Ablation can offer a possible “cure”, albeit via an invasive procedure.

In the meantime, you should not have excessive anxiety about this.  In the meantime, the following lifestyle interventions should help. Avoid stress, sleep deprivation, excessive amounts of caffeine. Consider starting stress reduction techniques like yoga, tai chi, and massage. If the palpitations recur in the presence of these symptoms, ask your physician if he thinks a beta-blocker medication like metoprolol can be used to “suppress your PAC’s”.  Also, if you have trouble sleeping, you may benefit from a polysomnogram ( a sleep study) as sleep disorders like obstructive sleep apnea (OSA) can be a source of arrhythmia. Also, your electrolyte problem (hypokalemia) needs to be corrected, as this is another common source of arrhythmia. A nephrologist (kidney specialist) is the expert in this area.
Thank you for your excellent question.

Sincerely,
Dr. S
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