= Dilated cardiomyopathy
{wiki}
\b[Dilated cardiomyopathy] is a form of <cardiomyopathy> involving enlargement of a ventricular chamber together with impaired pumping by the <heart> <muscle>. The <left ventricle> is a central site of the disorder, and other chambers can also be affected. Enlargement and pumping function are related but distinct observations; chamber size alone does not determine how much <blood> is expelled.<Cardiomyopathy Types by NHLBI>[Dilated cardiomyopathy: enlarged, weakened ventricles and reduced pumping]{ref}
A simple volume example makes that distinction quantitative. Let <end-diastolic volume> be $V_{\rm ED}$ and <end-systolic volume> be $V_{\rm ES}$. Then
$$
\mathrm{SV}=V_{\rm ED}-V_{\rm ES},\qquad
\mathrm{EF}=\frac{V_{\rm ED}-V_{\rm ES}}{V_{\rm ED}}.
$$
Here SV is <stroke volume> and EF is <ejection fraction>. A stipulated chamber changing from $200$ to $150\,\mathrm{mL}$ ejects $50\,\mathrm{mL}$ with EF $25\%$. Another changing from $120$ to $60\,\mathrm{mL}$ ejects $60\,\mathrm{mL}$ with EF $50\%$. A larger filled volume need not produce a larger <stroke volume>. These are constructed mechanical examples, not diagnostic cutoffs or reference ranges.
Imaging can test several parts of this mechanism. <Echocardiography> follows chamber dimensions and contraction; cine <magnetic resonance imaging> can quantify volumes and longitudinal motion. In a primary study, <Marcus Carlsson> and colleagues compared twelve patients with dilated cardiomyopathy, twelve controls and twelve elite triathletes. Their analysis combined atrioventricular-plane displacement with anatomical area to investigate the longitudinal contribution to ventricular pumping.<Atrioventricular plane displacement is the major contributor to left ventricular pumping in healthy adults, athletes, and patients with dilated cardiomyopathy by Marcus Carlsson and others>[Abstract, Methods: cine imaging and the three twelve-person groups]{ref}
This experiment illustrates why the condition cannot be represented by one chamber diameter alone: geometry, motion and transported volume supply different information. <Doppler echocardiography> and its <velocity-time integral> provide complementary flow observations, while a <clinical diagnosis> also requires the surrounding evidence and cause of the myocardial abnormality.
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