-MD is assoc w CM, usually DCM, along with conduction xx.
MD's with Clinical Cardiac Disease
Myotonic Muscular Dystrophy-
-Dystonic Myotonia 1 = CTG repeats at dystrophica myotonica protein kinase
-their kids can get congen DM, w a much more severe form bc more CTG's
-DM2- affects zinc finger prtn 9 gene
Dystrophin Defects-
-defic in dystrophin--> Duchenne MD (most sev form) w <3% dystrophin as Nl
--> Becker's MD- milder form bc more dystrophin
Emery-Dreiffus MD- x-linked rec in classic form, bc STA gene xx for emerin prtn in nuc membrane
-EDMD2 is auto dom, same Sx, bc mutation to LMNA gene, also affects inner nuc membrane...
...
Danon Disease- x-linked vacular CM and myopathy- bc xx to LAMP2 gene...
Assessment
ECG- asess for conduction xx
Holter- assess for conduction xx
Echo- pt may have kyphoscoliosis--> distort heart-lung relationship--> hard to assess
-check LV dimension, r/o dyskinesis and akinesis, check ant MV leaflet E pt septal separation, SF, EF, rate of wall contraction & relaxation
-check for DCM
Muscular Dystrophies with Cardiac Involvement
Dystrophinopathies
-DMD & BMD are related, but BMD less severe bc more dystrophin.
-w DMD can't walk by 12yo bc too little dystrophin
-bc DMD more likely to be sedentary--> less stress on heart, so less HF Sx and so HF doesn't manifest until pt has a major event; unlike w BMD who may present earlier w Sx of HF
Duchenne Muscular Dystrophy:
-usually well as neonate, then late to walk on their own, and Dx made by 3yo, and by school age they can't jump or run well and then can't climb stairs w/o handrail, and fall more often.
-Gower sign- to get up fr floor, they roll to prone and spread legs for balance, then lift butt first
-wheelchair by 12yo usually
-usually reduced IQ by 1SD fr Nl
-PE- big calfs, rubbery on palpation, weak neck muscles so can't raise head fr supine; weak proximal muscles worse than distal muscles. Eventually they can only move hands a little.
-if Diaphragm/intercostal xx--> poor cough, aspiration, pna...
-death by early 20s
-Cardiac Pathology-
-universal cardiac xx.
-epimyocardium is replaced by fat and then fibrosis starts in LV post wall behind post MV.
--> myocardial scarring progresses apically and then invades septum.
-doesn't usually affect RV or atria
-fibrosis--> dysfx, dilation, w thinning, then outpouching of LV post wall behind MV, then dev DCM
-Pt gets MR, +/- AR.
-then phtn fr LV failure, and then RV failure w PR/TR
-fibrosis/fatty infiltrate of conduction syst including SA and AV nds--> xx
-Cardiac H&P-
-few sx bc so inactive
-some w SOB, resp compromise bc of weak chest and diaph.
-some postural nocturnal dyspnea
-some palpation fr arrhythmias
-AVOID succinylcholine--> high K; other volatile anesthesia also cause xx, including malig hyperthermia rxn, rhabdo, masseter muscle spasms...
-+S3-4, pulm outflow murmur, JVD, hepatomegaly
ECG- deep Q at I, aVL, V5-6 +/- II, III, aVF
-often tall R precordial R wave w incr R/S ratio
-short PR often
-some w QT prolongation
-Holter- automaticity problems..., reduced variability in HR, AET, a-fib, 2nd/3rd HB, VT
Echo- epicardial thinning w DCM, espec at post LV wall..., disatolic dysfx, contraction abNly progressing inferiorly, MVP...
-Tx-
-Tx the Sx- digox, diuretics, AL reduction w ACEI espec if EF<55%
-beta-blockers for VT if needed, then c/s class III Rx- sotalol/flecainide, then c/s AICD
Duchenne Carriers
-ECG abNlies, similar to +DMD; some w DCM on echo... so c/s evaluating the female carrier
Becker Muscular Dystrophy
-stay ambulatory until 15yo or older (by convention/definition)
-cardiac sx don't correlate w skeletal muscle progression- can be sooner or later
-ECG similar to DMD pts...
--> DCM, some w RV dilation and then generalized DCM
X-linked Cardiomyopathy
-c/o tired, pain, cramping w exercise, without the weakness seen w DMD/BMD
-calf hypertrophy, elevated CK, no skeletal dystrophin xx, but do have abNl cardiac dystrophin
-dvp congestive CM, w death in 2yrs of onset Dx
-arrhythmias, AV block more common than DMD/BMD
-female carries can show HF too
Myotonic Muscular Dystrophy
-DM1 and DM2- inherited, auto dom
-sleep xx, GI xx w constipation and diarrhea, then get muscle weakness
-progressive facial muscle, temporalis, SCM, limb weakness distal>proximal (DDx DMD)
-cataracts
-conduction xx - brady, long PR, AVB, long QRS and QT, torsades, VT, VF, A-fib
-some w DCM
- +/- syncope and sudden death
Emery-Dreifuss Muscular Dystrophy
-elbow, Achilles tendon, post cx muscle contractures appearing before muscular humeroperneal weakness, w progressive bicep/tricep/ant tibial/peroneal muscle wasting; then knee, hib weakness, and eventually complete heart block.
-progressive fatty/fibrous deposits mainly at atria--> mechanical and electrical paralysis
-long PR, afib/flutter, brady, tachy, stroke fr atrial emboli
Facioscapulohumeral Muscular Dystrophy
-auto dom
-weakness at face, scapula muscles, distal LE muscles w weak hip/girdle muscles w assymetric weakness
-cardiac- seen in some w conduction xx
Limb-Girdle Muscular Dystrophies
-set of disorders...
-some w CM- DCM, nonspecific CM