I'm Jerry (@favoritepitch), 76 next month, early 2024 I ended up in the hospital 3 times for heart-related. No previous heart conditions though advised to start a low-dose statin at least a decade ago; didn't start but made some dietary changes; exercise was already way above average. Been feeling strange sensations in clavicle areas bilaterally, but attributed it to changes in exercise regiment. Jan 2024 at a wellness visit with PCP, after hearing of my reported (clavicle-area sensations and lightheadedness a couple days prior), hooked me to an EKG, reported that my usually around 50bpm HR was at 117 while sitting and displayed atril flutter; he rushed me to the nearest, best heart hospital. Treated for a-flutter in ER via medications, transferred to a unit and next day medication-induced stress test; cardiologist later reported scans looked "pretty good, no significant blockages." Prior to stress test, the physiologist specializing in cardiology took diet and exercise history. He said my history of serious endurance training (at least 50 years; soccer (college), mile runner and x-country in 9-12th grades, and high-volume cardio training for road-racing at 10Km to marathons, indicated research from the previous 15 years indicated I fall squarely in the category of long-term, endurance athletes who end up with cardiac arrhythmia(s) - in my case both a-flutter & then a-Fib. Discharged with various meds to continue. Four weeks later rushed to hospital with an MI; angioplasty and stent (thank you doc!). Four weeks after the MI my cardiologist was with me for a scheduled electro-cardioversion at "heart" hospital where I'd been rushed two months earlier. Cardioversion removed a-flutter and a-fib; 5 minutes from being discharged from hospital that same day, I was overcome with a feeling of something bad is happening to me. Shouted for help that I was "going down" and immediately flat-lined, was brought back, flat-lined again, brought back and rushed to emergency surgery for temporary pacemaker (thank you doc! - my cardiologist, for a second time within 8 weeks). Cardiac electro-physiologist (EP) came to me and said there were options, but her diagnosis was I had sick sinus syndrome (severe underlying conduction problem) that had been masked by my a-flutter and the cardioversion's removal of the a-flutter and a-fib enabled the SSS to "take over" causing the flatlining to happen (about two hours post-cardioversion). The EP strongly recommended I not leave the hospital without a permanent pacemaker. Got the pacemaker around 8-9pm that day. Between the pacemaker and the meds (especially metoprolol), my exercise has been cut back immensely though - not exceeding 70-75% max HR since then - March 2024. But thankful to be alive and able to exercise even at this level. I want to learn as much as I can about SSS: how is it diagnosed with certainty? what are the metrics, methods, and tests underpinning the diagnostics? I understand it is not curable. Will exercise actually accelerate further deterioration of the sino-atrial node and therefore SSS? And other related questions to SSS including could electro-cardioversion have caused damage to my sino-atrial node or other parts of my heart causing the "severe underlying conduction problem?" Grateful to be a part of this community at Mayo, to learn and share. 9/15/2026