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Farmacología Cardiovascular

Farmacología Cardiovascular . SISTEMA CIRCULATORIO: FUNCIONES PRINCIPALES. Transportar y distribuir sustancias esenciales a los tejidos Remover desechos metabólicos Ajustar la provisión de oxígeno y nutrientes en diferentes estados metabólicos Regulación de la temperatura corporal

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Farmacología Cardiovascular

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  1. Farmacología Cardiovascular

  2. SISTEMA CIRCULATORIO: FUNCIONES PRINCIPALES • Transportar y distribuir sustancias esenciales a los tejidos • Remover desechos metabólicos • Ajustar la provisión de oxígeno y nutrientes en diferentes estados metabólicos • Regulación de la temperatura corporal • Comunicación humoral

  3. Un sistema complicado

  4. Que se puede simplificar SERIES AND PARALLEL CIRCUITS

  5. CICLO CARDIACO

  6. 0 0 mv mv -80mv -80mv 0 mv -80mv Potencial de acción cardíaco ATRIUM VENTRICLE SA NODE time

  7. Conductacias del PA cardíaco

  8. Fast K reopens Slow K opens Fast K closes ("Delayed rectifier") Corrientes y PA cardíaco

  9. Del PA al ECG

  10. AV NODE AND AV BLOCKS FOCUS ON N REGION ECG NORMAL 1ST DEGREE PROLONGUED AV CONDUCTION TIME 2ND DEGREE 1/2 ATRIAL IMPULSES CONDUCTED TO VENTRICLES 3RD DEGREE VAGAL MEDIATION IN N REGION/COMPLETE BLOCK

  11. ENFERMEDAD CARDÍACA • Cardiovascular disease is the major cause of death • Cardiovascular function based on • Cardiac pumping ability • Pace-making electrical signals • Force of contraction • Height of ventricle discharge pressure • Integrity of vasculature • Presence of blockage • Muscular tone/structural integrity • Pressure drop needed to move blood to and through capillary beds • Blood volume/composition • Water, electrolyte, iron balances • Lipid and protein composition

  12. Patologías cardiovasculares que requieren farmacoterapia • Hipertensión • Arritmia • Falla cardíaca • Trastornos de flujo vascular

  13. I. Background to Hypertension -Regulation of Blood Pressure • Arterial blood pressure due to combination of cardiac output (CO) and total peripheral resistance (TPR) • CO – regulated by heart rate and stroke volume (CO = HR x SV) • TPR function of • Viscosity of blood (hematocrit) • Length of blood vessels • Blood vessel luminal diameter (especially precapillary arterioles)

  14. Cardiac Output • Heart rate • Function of • sympathetic, vagal nervous activity • Neuro-hormonal substances • 1° angiotensin II • 2º vasopression (anti-diuretic hormone = ADH) • Stroke volume • Function of • Venous return (function of venous tone [contractile state] and circulating blood (vascular) volume) • Venous tone function of sympathetic activity (α1, α2 receptors) • Vascular volume depends on • Intake of fluids (thirst) • Output of fluids (urine, sweat, etc) • Distribution of fluids (Starling’s law) • Myocardial contractility (MC proportional to sympathetic tone [β1 receptors])

  15. Characteristics of some adrenoceptors (sympathetic nerves) Tissues and effects receptors

  16. Autonomic Regulation of the Heart • Heart Rate • Parasympathetic input via vagus nerve causes decrease in HR (dominates) • Sympathetic input to sino-atrial node causes increase in HR (usually minor) • Heart contractility • Increased by sympathetic activity causing release of epinephrine, norepinephrine from adrenal gland

  17. Hipertensión

  18. Antihypertensive Classes • diuretics • beta blockers • angiotensin-converting enzyme (ACE) inhibitors • calcium channel blockers • vasodilators

  19. Alpha1 Blockers Stimulate alpha1 receptors -> hypertension Block alpha1 receptors -> hypotension • doxazosin (Cardura®) • prazosin (Minipress®) • terazosin (Hytrin®)

  20. Central Acting Adrenergics Stimulate alpha2 receptors inhibit alpha1 stimulation hypotension • clonidine (Catapress®) • methyldopa (Aldomet®)

  21. Peripheral Acting Adrenergics reserpine (Serpalan®) inhibits the release of NE diminishes NE stores leads to hypotension Prominent side effect of depression also diminishes seratonin

  22. Adrenergic Side Effects Common dry mouth, drowsiness, sedation & constipation orthostatic hypotension Less common headache, sleep disturbances, nausea, rash & palpitations

  23. Sistema renina-angiotensina

  24. ACE Inhibitors RAAS Angiotensin I ACE Angiotensin II 1. potent vasoconstrictor - increases BP 2. stimulates Aldosterone - Na+ & H2O reabsorbtion .

  25. Renin-Angiotensin Aldosterone System Angiotensin II = vasoconstrictor Constricts blood vessels & increases BP Increases SVR or afterload ACE-I blocks these effects decreasing SVR & afterload

  26. ACE Inhibitors Aldosterone secreted from adrenal glands cause sodium & water reabsorption Increase blood volume Increase preload ACE-I blocks this and decreases preload

  27. Angiotensin Converting Enzyme Inhibitors captopril (Capoten®) enalapril (Vasotec®) lisinopril (Prinivil® & Zestril®) quinapril (Accupril®) ramipril (Altace®) benazepril (Lotensin®) fosinopril (Monopril®)

  28. Calcium Channel Blockers • Used for: • Angina • Tachycardias • Hypertension

  29. Antagonistas de calcio como vasodilatadores

  30. Calcium Channel Blockers diltiazem (Cardizem®) verapamil (Calan®, Isoptin®) nifedipine (Procardia®, Adalat®)

  31. CCB Site of Action diltiazem & verapamil nifedipine (and other dihydropyridines)

  32. CCB Action • diltiazem & verapamil • decrease automaticity & conduction in SA & AV nodes • decrease myocardial contractility • decreased smooth muscle tone • decreased PVR • nifedipine • decreased smooth muscle tone • decreased PVR

  33. Side Effects of CCBs • Cardiovascular • hypotension, palpitations & tachycardia • Gastrointestinal • constipation & nausea • Other • rash, flushing & peripheral edema

  34. Diuretics Thiazides: chlorothiazide (Diuril®) & hydrochlorothiazide (HCTZ®, HydroDIURIL®) Loop Diuretics furosemide (Lasix®), bumetanide (Bumex®) Potassium Sparing Diuretics spironolactone (Aldactone®)

  35. Diuretic Site of Action . Distal tubule proximal tubule Collecting duct loop of Henle

  36. Mechanism • Water follows Na+ • 20-25% of all Na+ is reabsorbed into the blood stream in the loop of Henle • 5-10% in distal tubule & 3% in collecting ducts • If it can not be absorbed it is excreted with the urine •  Blood volume =  preload !

  37. Side Effects of Diuretics • electrolyte losses [Na+ & K+ ] • fluid losses [dehydration] • myalgia • N/V/D • dizziness • hyperglycemia

  38. Vasodilators • diazoxide [Hyperstat®] • hydralazine [Apresoline®] • minoxidil [Loniten®] • sodium Nitroprusside [Nipride®]

  39. Mechanism of Vasodilators • Directly relaxes arteriole smooth muscle • Decrease SVR = decrease afterload

  40. Nitratos como vasodilatadores

  41. Side Effects of Vasodilators • hydralazine (Apresoline®) • Reflex tachycardia • sodium nitroprusside (Nipride®) • Cyanide toxicity in renal failure • CNS toxicity = agitation, hallucinations, etc.

  42. II. Background to Arrhythmia - Rhythm of the Heart • Human heart is four-chambered • Chambers need to contract sequentially (atria, then ventricles) and in synchronicity • Also need relaxation between contractions to allow refilling of chambers • Above controlled electrically (Purkinje fibers allow rapid, organized spread of activation)

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