Ask him to roll over on his back, or other side, or position his arms so that they don't cause his shoulders to move towards each other. Then listen again. And tell David Not to Slouch!
Irregular Heart Beats can have LOTS of possible causes, most of them benign. Position is one possible explanation. So is the 'Electrical Rhythm' of the heart which can get 'discombobulated' by all the cutting, sewing, and general trauma of surgery. It can take several weeks to months for the Heart to "Settle Back Down" after surgery.
Premature Atrial Contractions (PAC's) and Premature Ventricular Contractions (PVC's) are quite common (and almost always benign). They can sound like a 'missed beat' but in actuality, one beat is moved up in time almost immediately after the previous beat. These can best be identified by an EKG or a 24 / 48 Hour Holter Monitor or 30 day Event Monitor.
Do you have a Stethoscope? I found I could pretty well 'guess' what kind of arrhythmia I was having by the sound / pattern once I was able to correlate the sound with the pattern. (PAC's / PVC's were "regularly irregular). I Quit going to the ER for Arrhythmias. (Doctors HATE it when patients do this, especially if they are right
Atrial Fibrilation can be wildly irregular and/or quite fast.
I called it a "Whack-o Heartbeat". A-Fib can cause clots to form. The usual protection is to prescribe Coumadin. Mechanical Valvers are already protected.
There a Several Different Types of Beta Blockers that can help control / prevent arrhythmias. Many of us are NOT fond of Doc's who prescribe Amiodarone (the Sledge Hammer of anti-arrhythmics) as their first line of defense (because it Works and it gets the patient out of the hospital or their office). Do a Search for Amiodarone if you want to find out why (for the Brave Only).
'AL Capshaw'