Lecture 8
Chapters 37 & 38
Cardiac Disorders
Cardiac Disorders
• System = heart, blood vessels (arteries & veins), Blood
• Blood rich w/ O2 & nutrients moves through vessels called arteries to narrower arteriols to capillaries where the rich blood is absorbed by bodies cells & waste products are absorbed (CO2, urea, Cr, ammonia) deoxygenated blood returned to circulation via venules to veins for elimination through lungs & kidneys
Cardiac disorders
• Heart =
* 4 chambers - R & L atria, R & L ventricles
* Blood from circulation to R atrium to R ventricle to pulmonary artery to lungs for gas exchange (CO2 & O2) to L atrium to L ventricle to aorta to systemic circulation
• Heart muscle = myocardium & surrounds the atria & ventricles
Cardiac Disorders
• Pericardium = fibrous covering around the heart that protects it from injury & infection
• Endocardium = 3-layered membrane that lines the inner part of the heart chambers
• Valves = 4 - two atrioventricular (tricuspid & mitral) & 2 semilunar (pulmonic & aortic) - control blood. flow between atria & ventricles & pulmonary artery & the aorta
Cardiac disorders
• Conduction = Generated & conducted by the myocardium - usually
* Originates in sinoatrial (SA) node - pacemaker
atrioventricular (AV) node bundle of HIS
purkinje fibers ventricular muscle tissue
contraction from apex upward forcing blood to lungs & circulatory system
Cardiac disorders
• Blood flow & Heart Rate (HR)
* Ave. HR = 60 - 80 beats/min. (adult)
* Ave. BP = 120/80 mm/Hg - resistance to blood flow through systemic arterial circulation
• Arterial BP determined by Cardiac Output (CO) = the volume of bld. expelled form the heart in 1 min. - calculated by mult. HR by stroke volume - Ave. CO = 4 - 8 l/min.
Cardiac Disorders
• Stroke Volume (SV) = amt. of bld ejected from the L vent. w/ each heart beat - Ave. = 70ml/beat
- SV determined by 3 factors:
-Preload - blood flow force that stretches the ventricle
- Contractility - force of ventricular contraction
- Afterload - Resistance to vent. ejection of blood caused by opposing pressures in aorta & systemic circulation
• Specific drugs can or preload & afterload, affecting both SV & CO - most vasodilators dec. preload & afterload a dec. in arterial pressure & CO
Cardiac DisordersCardiac Glycosides
• Digitalis - One of the oldest drugs (1200 AD)
- Effective in treating congestive heart failure (CHF)
- CHF = when the heart muscle weakens & enlarges loss of ability to pump blood through the heart & into the systemic circulation = heart failure (or pump failure)
- peripheral & lung tissues become congested = CHF
Cardiac DisordersCardiac Glycosides
• CHF can be left sided or right sided
• Cardiac glycosides = digitalis glycosides
- inhibits the Na - K pump inc. intracellular Ca
cardiac muscle fibers contract more efficiently
- Digitalis = 3 effects on the heart 1) + inotropic action (inc. myocard. contraction) 2) - chronotropic action (dec. HR) #) - dromotropic action (dec. conduction of the heart cells
Cardiac DisordersCardiac Glycosides
• The inc. in myocardial contractility = inc. card., peripheral, & kidney function by inc. CO, dec. preload, improving bld flow to periphery & kidneys, dec. edema, & inc. fluid excretion fluid retention in lung & extremities is decreased
• Digitals also used to correct atrial fibrillation & atrial flutter (cardiac dysrhythmias)
Cardiac Disorders Cardiac Glycosides
• Digoxin (Lanoxin) - Protein binding - low, t1/2 = 36 hrs - drug accumulation can occur
- monitor SE & serum levels closely
- metabolized by liver & excreted by kidneys - kidney dysfunction can affect excretion of dig.
- Do not confuse digoxin & digitoxin
- digitoxin = highly protein bound w/ a long t1/2 - seldom prescribed
Cardiac DisordersDigoxin (Lanoxin)
• Action = inc. myocardial contraction (+ inotrophy),
and slows HR (- chronotropy), therefore regulating the rate & rhythm of the heart
- Therapeutic serum levels = 0.5 - 2.0 ng/ml
• Use = moderate/severe systolic CHF, arrythmias
• SE = Dig. toxicity - bradycardia (pulse < 60), anorexia, diarrhea, N&V, blurred vision, lethargy - older adults more prone to toxicity
• DI - Other heart meds
Cardiac DisordersHeart Failure
• Other drugs =
* Vasodilators - dec. venous blood return to the heart & dec. cardiac filling, ventricular stretching & O2 demand
* Angiotensin-converting enzyme (ACE) inhibitors - dilate venules & arterioles & improves renal bld flow & dec. bld fluid volume
* Diruetics - first-line = reduces fluid volume
Cardiac DisordersAntianginal Drugs
• Used to treat angina pectoris ( acute cardiac pain caused by inadequate bld flow resulting from plaque occlusion in the coronary arteries of the myocardium or from spasms of the coronary arteries) - described as tightness, pressure in center of chest, pain radiating down L arm - attacks may lead to an MI
• 3 Types of angina pectoris
1. Classic (stable) - stress or exercise
2. Unstable (preinfarction) - frequently over day, severity
3. Variant (Prinzmetal, vasospastic) - during rest
Cardiac DisordersAntianginal Drugs
• Action - Inc. blood flow by inc. O2 supply, or by dec. O2 demand by the myocardium
• Nitrates, beta-blockers, calcium channel blockers
• Nitrates & calcium channel blockers effective in treating variant or vasospastic angina (not beta blockers)
• beta blockers effective in treating stable angina
• Non-pharm Rx = avoid heavy meals, smoking, extremes in weather changes, strenuous exercise, stress - Proper nutrition, moderate exercise, adequate rest & relaxation techniques
Cardiac DisordersAntianginals
• Nitrates - First agents used - Nitroglycerine (NTG)
- Action - acts directly on the smooth muscle of blood vessels = relaxation & dilation.
- Dec. cardiac preload & afterload & reduces O2 demand
- dilation of veins = less blood return to the heart
- dilation of arteries = less vasoconstriction & resistance
- Onset of Action
- sublingual (under the tongue) & IV = 1 - 3 min.
- transderm nitro patch = 30 - 60 min
Cardiac DisordersAntianginals
• SE = Headaches - less frequent w/ continued use, hypotension, dizziness, weakness, faintness
• Beta Blockers - Block the beta receptor site
Atenolol (Tenormin), Metoprolol tartrate (Lopressor), Nadolol (Corgard), Propranolol HCL (Inderal)
- Action - Dec. the effects of the sympathetic nervous system by blocking release of epi. & norepi dec. HR & BP reduce the need for O2 & the pain of angina
- Nonselective (beta-1 & beta-2) - Inderal, Corgard, Visken
- Selective (beta -1) - Tenormin, Lopressor
Cardiac DisordersAntianginals
• SE - Dec. in HR & BP
- Closely monitor vital signs
• Calcium Channel Blockers (Calcium Blockers) - Newest
Amlodipine (Norvasc), Diltiazem HCL (Cardizem), Nifedipine (Procardia, Adalat), Verapamil (Calan, Isoptin)
- Action - Ca activates myocard. contraction; inc. workload of heart. Calcium blockers dec. cardiac contractility (- inotropic) & the workload of the heart = dec. O2 need
Cardiac DisordersCalcium Blockers
• Use - long - term Rx of angina
• SE - Headache, Hypotension, dizziness, flushing of the skin
- Bradycardia w/ verapamil (Calan)
- Hypotension esp. w/ Nifedipine (most potent) - promotes vasodilation of coronary & peripheral arteries
• Calcium blockers can cause changes in liver & kidney function - Check liver enzymes periodically
• Can be given w/ nitrates to prevent angina
Cardiac DisordersAntidysrhythmics
• Cardiac dysrhythmia (arrhythmia) = any deviation from the normal rate or pattern of the heartbeat. HR’s too slow (bradycardia), fast (tachycardia), or irregular
• Electrocardiogram (ECG) identifies the type of dysrhythmia
- P wave = atrial activation
- QRS complex = ventricular depolarization
- T wave = ventricular repolarization
- PR interval = atrioventricular conduction time
- QT interval = ventricular action potential duration
Cardiac DisordersAntidysrhythmics
• Atrial dysrhythmias = prevent proper filling of the ventricles & dec. CO by 1/3
• Ventricular dysrhythmias = life threatening d/t ineffective filling of the ventricle = dec. or absent CO
• Dysrhythmias can occur - after an MI, from hypoxia (lack of O2 to body tissue), hypercapnia (inc. CO2 in the bld.), excess catecholamines (epi, norepi), or electrolyte imbalance
Cardiac DisordersAntidysrhythmic Drugs
• 2 major classifications of dysrhythmias
* Above bundle of HIS = supraventricular - A-flutter, a-fib., PAC’s
* Below bundle of HIS = Ventricular - PVC’s, Vent. tachycardia, V-fib.
• Desired action = restoration of normal cardiac rhythm
• 4 Classes:
• 1. Fast (sodium) Channel Blockers - dec. the fast Na influx to the cardiac cells, so - dec. conduction time of cardiac tissue, dec. likelihood of ectopic foci, inc. repolarization
- 3 subgroups of fast channel blockers
Cardiac DisordersAntidysrhythmics
• Class 1A - Procainamide (Pronestyl, Procan), Quinidine Sulfate (Quinidex) - slows conduction & prolongs repolarization
- Use = Control PVC’s, vent. tachycardia
- SE = Anorexia, headache, dizziness, weakness
• Class 1B - Lidocaine (Xylocaine), Mexiletine (Mexitil) -
Slows conduction & shortens repolarization
- Use = Ventricular arrythmias associated w/ acute MI’s
- IM & IV - IV bolus then a drip started (1 - 4 mg/min.)
Cardiac DisordersAntidysrhythmics
• Class 1C - Flecainide (Tambocor) - Prolongs conduction w/ little to no effect on repolarization
- Use - Life-threatening vent. dysrhythmias, supraventricular tachycardia, a-fib or flutter
• Beta Blockers - dec. conduction velocity
• Prolong Repolarization - Amiodarone (Cordarone) - emergency Rx of ventricular dysrhythmias. Inc. refractory perios & prolong action potential duration
• Calcium Channel Blockers - inc. refractory period of the AV node, dec. vent. response
Diuretics
• Used for 2 main purposed: decrease hypertension (lower BP), & decrease edema (peripheral & pulmonary) in CHF and renal or liver disorders
* Other uses = Dec. cerebral edema (Mannitol), dec. intraocular eye pressure (glaucoma), dec. ascities (liver disease)
• Used either singly or in combo to dec. BP & dec. edema
• Diuretics produce inc. urine flow (diuresis) by inhibiting Na & H2O reabsorption from the kidney tubules. Act on the kidneys in diff. locations to enhance excretion of Na (pg. 678)
Diuretics
• Every 11/2 hr. the total vol. of the body’s extracellular fluid (ECF) goes through the kidneys (glomeruli) for cleansing = 1st process for urine formation - sm. particles (electrolytes, drugs, glucose & waste) filtered in the glomeruli
• Normally 99% of filtered Na passing through glomeruli reabsorbed. 50 - 55% Na reabsorbtion in proximal tubules, 35 - 40% in loop of Henle, 5 - 10% in distal tubules, <3% in collecting tubules
• Diuretics that act on tubules closest to glomerule have greatest effect in causing natriuresis (Na loss in urine) - Mannitol
Diuretics
• Diuretics have an antihypertensive effect by promoting Na & H2O loss by blocking Na/Cl reabsorption = a dec. in fluid vol. & a dec. of BP
• With fluid loss - edema should decrease. When Na is retained, H2O also retained & BP increases
• Many diuretics cause loss of other electrolytes (K, Mg, Cl, bicarb)
• 5 categories of diuretics:
Action of Diuretics on Different Segments of Renal Tubules
DiureticsThiazides/Thiazide-like Diuretics
• Hydrochlorothiazide (Hydrodiuril, HCTZ), Metolazone (Zaroxolyn)
* Action - Distal tubules of the kidney to promote Na, Cl, & H2O excretion; acts directly on arterioles, causing vasodilation & BP; preload & CO = dec. vascular fluid & dec. in BP
* Use - Rx of hypertension & peripheral edema
* SE - Electrolyte imbalance (hypokalemia), hyperglycemia (inc. bld sugar), hyperlipidemia (inc. bld lipid level), dizziness, headaches, N&V
DiureticsThiazides
* CI - renal failure
* DI - Digoxin - if hypokalemia occurs, the action of digoxin is enhanced & dig. toxicity can occur
* Considered potassium - wasting - K supplements are frequently prescribed & serum K levels are monitored
Loop Diuretics - Act on the ascending loop of Henle by inhibiting Cl transport of Na into the circulation (inhibits passive reabsorbtion of Na)
- Potent & cause marked depletion of H2O & electrolytes
- Effect = dose related - dose & response
DiureticsLoop diuretics
• More potent than thiazides as diuretics, but less effective as antihypertensive agents
• Can renal bld flow up to 40%
• Have a great saluretic (Na-loosing) effect & can cause rapid diuresis vascular fluid vol. dec. in CO & BP
• Bumetanide (Bumex), Furosemide (Lasix) - derivatives of sulfonamides
• Furosemide (Lasix) -
* Use - Rx fluid retention/overload due to CHF, renal dysfunction, cirrhosis; hypertension; pulmonary edema
Diruetics Loop Diuretics
• Lasix (con’t) - used when other conservative measures fail (Na restriction & less potent diuretics)
* May be given IV or PO
* SE - Electrolyte imbalance ( esp. hypokalemia K < 3.5) & dehydration, orthostatic hypotension
* DI - digitalis preparations - dig. toxicity can result
* Nursing - Strict I & O, daily weights, vital signs, hydration status of client
Clients should be on K supplements, monitor serum K levels closely
DiureticsPotassium-Sparing Diuretics
• Weaker than thiazides & loop diuretics
• Action - act primarily in the collecting distal duct renal tubules to promote Na & H2O excretion & K retention
• Use - mild diuretics or in combo w/ antihypertensive drugs
• K supplements not used - serum potassium excess (hyperkalemia) results if K supplement taken w/ potassium - sparing diuretics
DiureticsPotassium - Sparing
• Spironolactone (Aldactone), Triamterene (Dyrenium)
• Aldactone (an aldosterone antagonist) - Aldosterone = a mineralocorticoid hormone that promotes Na retention & K excretion; Aldosterone antagonsits inhibit the Na-K pump (K retained & Na excreted)
• Amiloride (Midamor) - antihypertensive agent
• Triamterene - Rx of edema caused by CHF or cirrhosis
• K - sparing diuretics used alone = less effective than when combined with reducing body fluid & Na
- Usually combine w/ a potassium wasting diuretic
Diuretics Combination
• Combine a potassium sparing & potassium wasting diuretic = intensifies the diuretic effect & prevents K loss
• spironolactone & hydrochlorothiazide (Aldactazide)
• amiloride & hydrochlorothiazide (Moduretic)
• triamterene & hydrochlorothiazide (Dyazide, Maxide)
• When diuretic combinations are used, either combined in one tablet or as separate tablets, the dose of each is usually less than the dose of any single drug
• SE = hyperkalemia - caution w/ clients having poor renal function; do NOT use K supplements (unless K low)