What Rory McIlroy is dealing with is left ventricular hypertrophy, or thickening of the wall of the left ventricle (the most important ventricle) of the heart secondary to a viral infection. Viral infections unfortunately can wreak have on the heart, including causing inflammation, and causing disturbances with the electrical system of the heart. Viral infections can also cause many other long-term ramifications, including causing congestive heart failure and the need for a heart replacement/transplant. Viral myocarditis is the most likely diagnosis, and it sounds like at this point that the acute scary period is over, and his heart function remains stable.
Although we do not know the extent of the damage to both the electrical activity as well as the ability to pump. A normal heart averages about 60% pumping efficiency; several diseases can cause the heart to pump less efficiently, including with viral infections. Sometimes these drops are temporary and sometimes they are permanent. If the heart’s pumping ability drops significantly, say as low as 15 to 20%, this in turn can cause some abnormal electrical impulses also known as cardiac arrhythmias. Sometimes patients need to have pacemakers or defibrillator implanted to override the hearts natural electrical system and to take over pumping for the heart. The best way to monitor the pumping ability of the heart is with an echocardiogram, basically an ultrasound of the heart. Here is a good link that can discuss viral infections of the heart: www.healthline.com/health/heart-disease/viral
