Physiological changes in myocardial function seen in heart failure

Physiological changes in myocardial function seen in heart failure

Acute effects of moderate heart failure

1) Acutely damaged heart—>

i) reduced cardiac output

ii) increased systemic venous pressures

2) Compensation —>

i) sympathetic stimulation:

a) increased force of contraction

b) increased heart rate

c) increased tone of large veins —> increased MSFP

ii) dilatation:

Frank-Starling law —> increased contractility

Chronic stages of heart failure

1) Recovery of myocardium

i) hypertrophy

ii) increased collateral blood supply

(final stages within 4-6 months; if adequate will see an associated reduction in sympathetic stimulation)

2) Renal retention of fluid [via reduced GFR, rein-angiotensin. aldosterone]

i) beneficial [moderate retention]: increased VR —> improve CO

ii) detrimental [excess retention]: a) overstretching heart

b) pulmonary congestion

c) peripheral oedema