ABFM HEART FAILURE PATHOPHYSIOLOGY SUMMARY 2024

1. Post MI remodeling: Postinfarction remodeling divided into 2 phases: a. early phase (wi 72 hrs): i. expansion of infarct zone, resulting in wall thinning, ventricular dilatation diastolic & systolic wall stresses. ii. activation renin-angiotensin system iii. production of atrial & brain natriuretic peptides (ANP & BNP). b. late phase ( 72 hrs). involves LV more globally w time-dependent dilatation, distortion of ventricular shape, mural hypertrophy (an adaptive response) to offset load, attenuate progressive dilatation, stabilize contractile fxn. i. By 4 weeks post MI, the affected myocytes are replaced by fibrous tissue. ii. Myocardial reperfusion does improve late-phase regional and global ventricular fxn. 2. subclinical hypothyroidism has long been assoc with cardiac dysfxn. a. subclinical hypothyroidism (TSH 4 µU/L w nl or borderline low thyroid hormone) can cause LV systolic & diastolic dysfxn, which improves w thyroid replacement tx. b. Thyroxine can exacerbate CAD, start low dose, titrated slowly in pts w underlying CAD. c. Tx subclinical hypothyroidism