Lecture 10 Flashcards
Define heart failure
Failure of the heart to pump enough blood to satisfy the body’s requirements. Acute or chronic Characterized by a clinical syndrome involving a characteristic pattern of hemodynamic, renal, neural, and hormonal responses. Heart failure is considered a multisystem disorder.
Causes of heart failure
Diminished coronary blood flow (ischemic heart disease) Damaged heart valves thyrotoxicosis Vitamin B deficiency Cardiac muscle disease
What are the acute effects of moderate heart failure?
Sudden damage (MI) Reduced cardiac output → fatigue Fall in arterial pressure Damming of blood in veins → congestion RESULT: compensation
What is the role of sympathetic reflexes in heart failure compensation?
Baroreceptor that measure arterial pressure Detect fall in BP NET EFFECT Sympathetic nervous system activated Parasympathetic nervous system inhibited TLDR: fall in CO, body compensates by increase CO n BP Direct effect on the heart SNS speeds up the heart n contractility of the heart (positive ionotropic effect) Positive ionotropic n chronotropic Increases venous return [causes blood vessel constriction] → more blood cmng to the heart → increases cardiac output → raises filling pressure
What is the effect of heart failure on the Starling curve?
Increase filling pressure → bigger CO Stretching the muscles fibers of the myocardium When they contract, they push out more blood More preload (blood cmng back to the heart in the vein) → shift along the curve Sudden fall in BP [lack of CO] → curve shift to the right [more filling pressure bc constricting the vein] Sympathetic nervous system increases contractility → efficiency of pumping increased For given pressure, more CO Direct effect of sympathetic nervous system by beta receptors Pushes the curve upwards Fall in CO → body compensates in short term by shifting along the curve n shifting curve up Result net increase in CO for increase filling pressure
How does the baroreceptor reflex compensate for a decrease in BP?
Decrease in BP [fall in CO] detected by baroreceptors in carotid sinus n aortic arch Reduces number of nerve impulses in vasomotor centers in medulla Inhibits parasympathetic nervous system Activates SNS Increase heart rate n contractility Increase vasomotor tone (constricts blood vessels) -> increases TPR n venous return More pressure for the heart to push against can help compensate in short term but may be damaging in the long term When the heart fails, makes the heart work harder -> can be damaging
What is the role of fluid retention in heart failure compensation?
Long term try n increase fluid retention Retention of fluid by kidneys -> reduced urine output via release of aldosterone n ADH Effects of aldosterone n ADH Increased blood volume -> increased venous return -> increased systemic filling pressure Reduces venous resistance which eases flow of blood to the heart Moderate fluid retention is beneficial Large amt of fluid retention is not beneficial
What are the causes of reduced renal urine output?
Decreased glomerular filtration Caused by a fall in arterial pressure Renin-angiotensin system Aldosterone secretion
What are the aims of treating CHF?
Relieve symptoms Improvise exercise tolerance Reduce acute exacerbations Reduce mortality
What are some first line treatments of chronic CHF?
ACE inhibitors Angiotensin II receptor antagonists β-adrenoreceptor blockers
What are some second line treatments of chronic CHF?
Aldosterone antagonist (spironolactone) Cardiac glycosides (digoxin) Increase heart contractility
What do ACE inhibitors and angiotensin II receptor antagonists do and what are some examples?
ACE inhibitor: enalapril Angiotensin II receptor antagonists: candersarta FUNCTION Reduce peripheral resistance (afterload) Stop angiotensin II vasoconstriction Reduce blood volume (preload) via reducing aldosterone release Increase K+ concentration counteracting loss via diuretics Helps to prevent cardiac remodeling Increase in size Strong evidence that they increase survival
What do β-adrenoreceptor blockers do and what are some examples?
EXAMPLES: bisoprolol n carvedilol Reduce the work of the heart n slow disease progression Reduce renin-angiotension-aldosterone Some also block α receptors on blood vessels leading to vasodilation Start at low dose n slowly titrate Only use in stable heart failure Can shift along the curve w/o changing CO Reducing work of the heart
What do cardiac glycosides do?
Block Na+/K+ exchange → greater Ca2+ influx via Na+/Ca2+ exchanger → increases myocardium contractility Suitable for patients w CHF n atrial fibrillation Worsening or severe heart failure due to left ventricular systolic dysfunction despite ACE inhibitor, β-blocker n diuretic therapy
What is ivabradine?
Used to treat angina Slows heart by direct action on SA node Probably blocks pacemaker current (If) Increases filling time n CO
How to treat intractable heart failure?
Transplantation Ventricular assist device (VAD) Mechanical pump that pumps blood thru the body
