 So, let's contrast a dilated cardiomyopathy with another cardiomyopathy, a hypertrophic obstructive cardiomyopathy, also known as HOKUM, hypertrophic obstructive cardiomyopathy, HOCM. So, as you see in this picture over here, our normal heart is on the top, and then our hypertrophic heart is on the bottom. You can see these very, very, very large muscular walls and intraventricular septum here of the left ventricle specifically. We're seeing a marked ventricular concentric hypertrophy, so this is all the way around the heart where the muscle fibers are hypertrophying. So what we have here is a predominately septal hypertrophy as well as systolic anterior motion of those mitral valve leaflets, and that causes an outflow obstruction. That outflow obstruction will then lead to shortness of breath or dyspnea and even possible syncope. A common presentation for HOKUM, or hypertrophic obstructive cardiomyopathy, is an athlete or a young male that passes out, undergoes a syncable episode while on the sporting field, and that's typically the clinical presentation you'll see often on the USMLE. How else do these patients present? They can have an S4 heart sound that occurs right before the S1 heart sound during systole, and then they also will see a systolic murmur. You do have a potential for a mitral regurge due to that outflow obstruction that we talked about just a minute ago, and in contrast to dilated cardiomyopathy, the sarcomeres and a hypertrophic obstructive cardiomyopathy are added in parallel. So if you remember back into your physics, parallel, meaning that they're moving together, so you're going to have multiple sarcomeres on top of each other, that's how we get that hypertrophy, versus series when we're adding them together alongside of each other, like so. A majority of the cases of hypertrophic obstructive cardiomyopathy are actually familial. A lot of times these are autosomal dominant gene coded. So the specific gene that is encoding this familial trait is a gene for sarcomere proteins. This leads to a diastolic dysfunction, and oftentimes we see syncope during exercise. Like I mentioned earlier, typically we're going to be talking about an athlete that's on the practice field, or during a game, they're working very, very hard, their heart just can't keep up pumping out the blood that it needs to to supply the body with the essential nutrition and oxygen, and they undergo syncope. That syncopal episode also increases their potential to have a ventricular arrhythmia. This ventricular arrhythmia is what could lead to a sudden cardiac death. So these young athletes that are working an unknown hypertrophic obstructive cardiomyopathy, then they can actually undergo syncope, arrhythmia, and potentially death. So that's why we always need to be aware of this and aware of the treatments. So what are the treatments? First and foremost, if we know a patient has a Holcomb case, then we're going to have them no longer participate in high intensity athletics. This can be a problem for patients that are very, very athletic, and they're very talented and being told to no longer be able to participate in these athletic events can be very, very traumatizing. We'll also treat them with beta blockers or a non dihydropyridine calcium channel blocker like verampimil. And one thing that we always need to be aware of with these type of patients is that we can use an ICD, specifically an automated one, if syncope occurs. This is why you see these ICDs all around in public now and in schools and in athletic events and trainers and everything carry these because if a patient does go down and we can get an ICD onto them and find out they are in arrhythmia, we can shock them back into rhythm if it's a shockable rhythm and potentially keep them from dying. So this is a very, very important piece of equipment to be aware of and be able to get to quickly and to know that this is a necessary item.