Dilated cardiomyopathy (MC)

Primary causes

  • Idiopathic (~50%) = family HX

    • Hemochromatosis (labs show elevated Fe and liver enzymes) ➔ restrictive or dilated

    • MYH7 mutations ➔ altered β-heavy chain

    • TTN gene mutations ➔ altered titin protein which is involved with sarcomere springing back

Secondary Causes

  • Viral infections ➔ myocarditis: Coxsackiesvirus B, Lyme, chagas (a parasite), rheumatic heart disease

  • Too much fun: Cocaine, etOH, etOHism ➔ "wet beriberi" (deficiency in B1 - thiamine)

  • Chemo (Doxorubicin) & radiation

  • Pregnancy: last trimester or up to 6mo postpartum

  • Heart: Tachyarrhythmias, ischemia; Valvular: aortic stenosis/regurgitation, MV regurgitation ➔ blood leaking back into ventricle

  • Inflammation: Sarcoidosis, SLE

  • Virus goes right into cardiomyocytes ➔ cytotoxicity or virus causes autoimmune response

    • Lyme usually causes conduction issue (AV block)

  • Sarcoidosis causes a reversible DCM

PATHO

  • STRETCHED HEART SUCKS AT PUMPING. STRETCHING ➔ CONDUCTION & VALVE PROBLEMS

  • ↑ PRELOAD ➔ dilated LV ➔ eccentric hypertrophy ➔ systolic dysfunction

  • Left HF eventually ➔ Right HF

  • Cardiac myocyte issue (from infection/toxin) or tachyarrhythmia ➔ ↓ contractility ➔ compensation to keep up cardiac output ➔ ↑ preload

  • Blood going back into ventricle (mitral/aortic regurgitation) ➔ ↑ preload

↑ end-diastolic volume/EDP (PRELOAD)

  • ↑ preload ➔ eccentric remodeling (sarcomeres are added in series to existing sarcomeres)

  • ➔ ↓ myocardial contractility ➔ ↓ ejection fraction (systolic problem)

    • For funzies:

      • Chronic HTN or aortic valve stenosis ➔ concentric hypertrophy (stiff) (new sarcomeres added in-parallel to existing sarcomeres)

      • ↑ Wall thickness ➔ impaired filling ➔ diastolic dysfunction

SSX

  • Left sided then eventually right sided Systolic HF

    • Dyspnea on exertion, orthopnea

    • Rales, cardiac wheeze

  • S3 (early diastole) lub-dadub

  • Displaced PMI

  • HX of MR murmur (because that caused the dilated ventricle)

  • Palpitations from conduction issue

  • S3 occurs during rapid-passive filling at the start of diastole.

    • Once enough blood pools in atria the trap door (valve) opens and dumps the blood into a dilated ventricle

      • I think of it like an echo in a canyon

    • Athletes have a "healthier" eccentric remodeling and pregnant pts have a little bit more volume (S3 maybe normal finding in these pts)

    • S4 - "lalub-dub" happens with active filling (when the atria give that last little squeeze) late in diastole

  • Big left ventricle moves (displaces) maximal impulse from 5th intercostal at mid clavicular line toward axillary line

    • Diameter: discrete/≤ 2 cm ➔ > 3 cm (signals left ventricular enlargement)

    • Amplitude: brisk and tapping ➔ diffuse low-amplitude (hypokinetic)

    • Duration: ≤ 2/3 of systole ➔ sustained

Little bit of a HF reminder:

  • Systolic dysfunction (stretched heart) ➔ forward failure

    • ↓ output ➔ shocky (hypotension, cold peripheral)

  • Backed up left side means the pulmonary circulation is backed up ➔ backward failure

    • ↑ pulmonary vein pressure ➔ pulmonary congestion ➔ fluid forced into interstitium (extravasated)

DX

  • DX with ECHO - Ventricular dilatation, ↓ systolic function (↓ EF), local/global hypokinesia (wall motion abnormalities)

  • CXR: cardiomegaly, pulmonary edema

  • ↑ BNP, CK-MB and troponin to r/o MI

  • EKG may show some conduction issues (a-fib, AV-block, LBB) low voltage or ∆ cardiac axis

  • Echo shows function (ejection fraction) and extent of remodeling

    • Doesn't help with etiology so if it seems idiopathic and you're asked to find the cause... you might want to answer something about genetics.

TX

  • TX underlying: tell them to stop drinking, give thiamine, treat infection

  • TX systolic HF: ACEi/ARB, diuretics, β-blockers, digoxin

    • Propanolol does not have "proven" benefit in HF

  • AICD (Automated Implantable Cardioverter/Defibrillator) if EF < 35%

  • Acute HF: Sit them up, diuresis if pressure > 90mmHg, positive pressure ventilation (BVM/CPAP/intubate)

  • Anticoagulation for a-fib/valvular issues

  • Don't pick digoxin unless all of the other choices are definitely wrong

  • Heart transplant if all else fails

  • Click here for more on acute CHF