Definition
• Acquired or inborn state in which the heart cannot meet metabolic demands of the body at nml physiologic venous pressures
• Accounts for ∼10% of pediatric heart transplant, w/ DCM as most common cause
Pathophysiology
• Preload = loading force on the heart (amt of venous blood return) that stretches myocardial fibers, which (to a point) results in ↑ contraction strength and thus ↑ cardiac output (represented by Frank–Starling law) (Pediatr Rev 1980;1:180)
• As filling pressures ↑ beyond point of maximal contractile response, myocardial contraction becomes increasingly inefficient, resulting in ↓ cardiac output
• As tissue perfusion impaired 2/2 ↓ cardiac output, renin–angiotensin sys activated resulting in ↑ renal Na & H2O retention → ↑ extracellular volume & cardiac preload
• Response, while initially adaptive, is maladaptive in the long run → ↑ afterload against which the heart must work and results in volume overload
Etiology (Pediatr Rev 1980;1:321; Heart 2002;88:198)
• Increased demand for cardiac output (high-output cardiac failure)
• Hypermetabolic states: Hyperthyroidism, anemia, sepsis
• Valvular insufficiency: Can be inherited or acquired
• Fluid overload: Renal disease or iatrogenic
• Left- to right-sided shunting: PDA, VSD, ASD, etc.
• Increased afterload
• Aortic or pulmonic valvular stenosis
• Coarctation of the aorta, pulmonary artery stenosis
• Systemic or pulmonary hypertension
• Impaired myocardial function/contractility
• Myocarditis: Lymphocytic myocarditis accounts for 10% of recent onset CM
• Viruses, most common causes in dev countries; coxsackie B and adenovirus
• Chagas disease is the most common cause in C. and S. America
• Dilated cardiomyopathies: 1° indication for xplant aside from CHD in infancy
• Prognosis for DCM is 60% at 5 yr from presentation
• DCM genetic etiology at present a “molecular maze”; mutations assoc w/
cytoskeleton, troponin T, and other sarcomere protein genes
• Coronary artery disease, rare aside from anomalous cardiac vasculature or high-risk patients (ESRD, familial hyperlipidemia, DM, etc.)
• Metabolic abnormalities (Pompe disease)
• Nutritional or toxic insults (thiamine deficiencies, chemotherapeutics)
• Electrolyte disturbances
• Dysrhythmias
History and Physical Exam
• Hx poor feeding, poor weight gain, sweating w/ feeds, poor exercise tolerance, cyanosis, chest pain, nocturnal cough, orthopnea, paroxysmal nocturnal dyspnea
• Physical exam may reveal tachycardia or tachypnea
• Edema not common; in infants, assess eyelids & sacrum (most dependent areas)
• Heart may be enlarged w/ displaced point of max impulse
• Heart murmur may be present, as may extra heart sounds (S3, S4, etc.)
• Crackles on pulmonary exam indicate pulmonary edema with left-sided failure
• Elevated jugular venous pulsations or enlarged liver seen with right-sided failure
Evaluation (Heart 2002;88:198)
• EKG rarely nml but very nonspecific, CXR may have cardiac enlargement, pulm edema
• BNP (normal values vary with age)
• Echocardiography can assess cardiac function and for anomalous coronary anatomy
• Myocarditis: Viral PCR (coxsackie, adenovirus, echo, influenza, parainfluenza, VZV, RSV, rubella, CMV, EBV, HIV, parvovirus, Mycoplasma, and other endemic infections such as Chagas, dengue, diphtheria, Coxiella), troponin, CBC (for lymphocytosis), and myocardial bx for histology and PCR, toxicology (cocaine)
• Autoimmune: Anti-Ro and La, ANA, RF, ESR, dsDNA, and other autoantibodies
• Mitochondrial: Carnitine, acylcarnitine, lactate, glucose, CBC (for neutropenia), urine AA for methylglutaconic aciduria, muscle bx, molecular genetics (Barth syndrome)
Treatment (Heart 2002;88:198)
• Pharmacokinetics in pediatrics not as clear for the core CHF drugs
• ACE inhibitors: 1 retrospective study demonstrating reduced mortality in children w/ DCM compared to standard Rx with digoxin and diuretics. (Pediatr Cardiol 1993;14:9)
• BB: In children, 2 RCTs have shown improvement of LV fx, inc exercise tolerance
and dec need for heart xplant in idiopathic, drug-induced, or inherited DCM.
(Heart 1998;79:337; J Heart Lung Transplant 1999;18:269)
• Diuretics: Clear clinical benefit but little published in the last 30 yr
• Chlorothiazide, ethacrynic acid, and furosemide are all used
• Spironolactone; small RCT in peds showed safety and efficacy; no mortality impact
• Use derived from benefit seen in larger RALES study in adults
• Digoxin: Long-standing corner stone of pediatric CHF management
• Only studies published that evaluate efficacy of digoxin in children show modest benefits in small nonrandomized or unblinded trials (all were in infants w/ large VSDs) (Am J Cardiol 1999;83:1408; Am J Cardiol 1991;68:1377)
• Increased contractility does not consistently correlate with clinical improvement
• Oldest core of CHF therapy is digoxin and diuretics, now w/ data supporting use of ACE-Is and BB as well as spironolactone