Restrictive Cardiomyopathy

00:01 The final category of cardiomyopathy is restrictive cardiomyopathy.

00:05 Restrictive cardiomyopathies are fundamentally a diastolic dysfunction cardiomyopathy.

00:12 So in some respects, it share some of the features with hypertrophic cardiomyopathy.

00:16 Overall, it is the least common of all three types - dilated, hypertrophic and restrictive, about 5% overall, or less.

00:26 What's been indicated on the schematic is that the myocardium has been partially replaced with something else that isn't myocardium.

00:35 Fundamentally, this makes the wall less able to dilate and fill, it makes it stiffer.

00:42 As a result of that, we do not have normal filling of the left ventricle.

00:48 Sitting behind the left ventricle, his left atrium, it's trying to squeeze blood into that very stiff left ventricle and it's not being successful.

00:56 So you have a volume overload leading to dilation of the left atrium.

01:01 So in words, what I just said, you get stiffening of the ventricular wall, loss of myocardial flexibility, contractile force, due to infiltration by abnormal tissues.

01:13 This can also occur not only due to the infiltration with things like amyloid, but also due to scarring of the pericardium.

01:22 So that would be a constructive cardiomyopathy if we have fibrous connective tissue, completely surrounding the heart that will also keep the heart from being able to fill during diastole.

01:33 And we'll have a similar physiologic manifestation.

01:39 What are the causes? Like everything in medicine, idiopathic is always on your differential, meaning we don't know.

01:46 I suspect, as we get smarter and more clever and are able to do deep sequencing, we'll find more genetic basis for this.

01:55 There are various familiar forms of restrictive cardiomyopathy with known genetic mutations, we'll briefly touch on those.

02:04 But most commonly, as causes, restrictive cardiomyopathy are the deposition of other non-cardiac proteins.

02:14 Chief amongst these is amyloid.

02:16 We'll talk more about that.

02:17 But sarcoid can also be a cause of restricted cardiomyopathy.

02:21 If you've been paying attention, you're saying, 'Wait, you said sarcoid could be dilated cardiomyopathy? Yep, it can.

02:27 In some cases, because of the scarring and the deposition, you can also get a restrictive cardiomyopathy.

02:33 Hemochromatosis can also cause a restrictive cardiomyopathy.

02:38 Initially, it will prominently present as a dilated cardiomyopathy due to apoptosis due to iron overload, reactive oxygen species, et cetera.

02:47 But with time, you can get fibrosis so it can become a restrictive cardiomyopathy, And then Loeffler's endomyocarditis.

02:55 A rare but interesting form of restrictive cardiomyopathy due to thickening fibrosis of the endocardial layer.

03:05 In restricted cardiomyopathy, fundamentally, there's some increased extracellular material not otherwise specified in the myocardium.

03:13 Or you can have endocardial scarring, the lining of the ventricular walls become fibrotic.

03:21 That will also keep the wall from being able to fill during diastole.

03:26 You have decreased diastolic relaxation, and decreased ventricular filling, the consequences are due to a stiffened ventricular wall.

03:36 And upstream, we're going to get atrial dilation.

03:39 That poor atrium, left atrium is trying to squeeze blood into that stiff left ventricles like, can't get anywhere, so you get atrial dilation..

03:48 With that happening, you can get systemic venous congestion.

03:53 Basically, the increased pressure and volume overload in the atrium reflects back through the lungs and into the systemic vasculature.

04:00 So you can see left heart failure, right heart failure, biventricular failure.

04:07 There's also diminished cardiac output.

04:09 Clearly, you're not filling the ventricles, so you're not getting the maximum amount of volume out so patients can also present with hypotension.

04:18 The configuration is different than what we saw in dilated or in hypertrophic cardiomyopathy.

04:23 This is not a floppy heart.

04:24 This is not a muscular heart.

04:26 This is kind of a normal-sized chamber, but the nature of what's in the walls makes it stiff.

04:34 The atria will dilate up, and that's an important component of a restrictive cardiomyopathy.

04:41 This is just showing you an example of restrictive cardiomyopathy due more to the endocardial fibrosis.

04:48 The wall may actually not have much in the way of extracellular material, but the endocardium being fibrosed limits the movement of that wall.

05:00 What are the signs and symptoms? Well, you can predict based on what you now know about the pathophysiology.

05:05 You have poor forward flow so patients are dizzy, lightheaded, they may have frank syncope.

05:10 They may have left heart failure, so they are dyspneic.

05:14 You can also, as part of that dyspnea and the pulmonary edema have rales.

05:19 You can also have diminished flow into the coronary artery, so you have angina and you can have arrhythmias.

05:26 So all the things again, kind of just because you have this doesn't necessarily mean that you have a restrictive cardiomyopathy.

05:33 Clearly it could be dilated cardiomyopathy, hypertrophic cardiomyopathy or some other cause.

05:40 But these are signs and symptoms associated with that.

05:43 And you may also see a systolic heart murmur.

05:47 So abnormal flow through the valve because of poor filling of the heart.