Chapters 37

1
Lecture 8

• Chapters 37 38
• Cardiac Disorders

2
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

3
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

4
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

5
Right Ventricle
6
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

7
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.

8
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

9
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

10
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

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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)

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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

13
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 lt 60),
  anorexia, diarrhea, NV, blurred vision, lethargy
  - older adults more prone to toxicity
• DI - Other heart meds

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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

15
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

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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

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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

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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

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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

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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

21
Cardiac DisordersAntidysrhythmics

• Cardiac dysrhythmia (arrhythmia) any deviation
  from the normal rate or pattern of the heartbeat.
  HRs 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

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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

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Cardiac DisordersAntidysrhythmic Drugs

• 2 major classifications of dysrhythmias
• Above bundle of HIS supraventricular -
  A-flutter, a-fib., PACs
• Below bundle of HIS Ventricular - PVCs,
  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

24
Cardiac DisordersAntidysrhythmics

• Class 1A - Procainamide (Pronestyl, Procan),
  Quinidine Sulfate (Quinidex) - slows conduction
  prolongs repolarization
• - Use Control PVCs, vent. tachycardia
• - SE Anorexia, headache, dizziness, weakness
• Class 1B - Lidocaine (Xylocaine), Mexiletine
  (Mexitil) -
• Slows conduction shortens repolarization
• - Use Ventricular arrythmias associated w/
  acute MIs
• - IM IV - IV bolus then a drip started (1 -
  4 mg/min.)

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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

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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)

27
Diuretics

• Every 11/2 hr. the total vol. of the bodys
  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, lt3 in collecting tubules
• Diuretics that act on tubules closest to
  glomerule have greatest effect in causing
  natriuresis (Na loss in urine) - Mannitol

28
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

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Action of Diuretics on Different Segments of
Renal Tubules
30
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, NV

31
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

32
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

33
Diruetics Loop Diuretics

• Lasix (cont) - used when other conservative
  measures fail (Na restriction less potent
  diuretics)
• May be given IV or PO
• SE - Electrolyte imbalance ( esp.
  hypokalemia K lt 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

34
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

35
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

36
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)