Heart Blood Flow and Cardiac Mechanics

Blood Flow Through the Heart

• The superior vena cava brings deoxygenated blood from the upper body to the Right Atrium (1)
• Deoxygenated blood flows through the Tricuspid valve to the Right Ventricle (2)
• The right ventricle pumps deoxygenated blood through the pulmonary valve to the pulmonary artery (3)
• The pulmonary artery carries deoxygenated blood to the lungs where it receives oxygen (6)
• Oxygenated blood returns from the lungs to the Left Atrium via the Pulmonary veins (4)
• Blood flows through the Mitral valve to the Left Ventricle (5)
• The left ventricle pumps oxygenated blood through the aortic valve into the aorta which distributes it to the body

Mechanical System

• Systole is the contraction of the myocardium
• Diastole is the relaxation of the myocardium
• Cardiac output is the amount of blood pumped by each ventricle in 1 minute
• Cardiac output (CO) is calculated by multiplying stroke volume (SV) by heart rate (HR)
• Cardiac index is another measure of heart function but the information is not provided

Factors Influencing Blood Pressure

• Blood pressure equals cardiac output multiplied by systemic vascular resistance
• Systemic vascular resistance is affected by dilation of blood vessels, and the amount of blood pumping through the heart.

Evidence Based Guidelines for Blood Pressure Management

• Blood pressure is assessed in four stages
• Normal
• Elevated
• Stage 1
• Stage 2
• Hypertensive Crisis
• Elevated systolic blood pressure is associated with heart failure, stroke, and renal failure
• Prehypertensive blood pressures are no longer considered "high normal"
• Lifestyle modifications are necessary to prevent cardiovascular disease
• Thiazide-type diuretics are the initial drug therapy for most patients with hypertension
• These diuretics reduce the volume of blood being pumped

Etiology of Hypertension

• Primary hypertension is elevated blood pressure without an identified cause
• Primary hypertension accounts for 90% to 95% of all cases
• Contributing factors to hypertension
• Increased sodium-retaining hormones and vasoconstrictors
• Diabetes mellitus
• Higher than ideal body weight
• Increased sodium intake
• Excessive alcohol intake

Risk Factors for Primary Hypertension

• Age increases the risk as vessels become more rigid
• Alcohol consumption
• Cigarette smoking
• Diabetes mellitus changes elasticity of vessels
• Elevated serum lipids
• Excess dietary sodium
• Gender
• Family history
• Obesity
• Ethnicity
• Sedentary lifestyle
• Socioeconomic status
• Stress

Pathophysiology of Primary Hypertension

• Genetic factors have little contribution to blood pressure levels in the general population
• Stress and increased sympathetic nervous system activity
• Produce increased vasoconstriction Increase heart rate Increase Renin release
• Water and sodium retention High sodium intake may activate pressor mechanisms, resulting in water retention Certain demographics are associated with "salt sensitivity."
• Obesity
• Increasing age
• African American ethnicity
• Insulin resistance and hyperinsulinemia High insulin concentration stimulates SNS activity and impairs nitric oxide-mediated vasodilation Results in elevated blood pressure

Etiology of Secondary Hypertension

• Secondary hypertension is elevated blood pressure with a specific cause
• Secondary hypertension accounts for 5% to 10% of adult cases
• Contributing factors: Coarctation of aorta Renal disease Endocrine disorders due to hormone imbalances Neurologic disorders Cirrhosis Sleep apnea

Hypertension Clinical Manifestations

• Development is very insidious
• Patients are frequently asymptomatic until target organ disease occurs
• Symptoms are often secondary to target organ disease
• Symptoms can include: Fatigue, reduced activity tolerance Dizziness Palpitations, angina Dyspnea

Hypertension: Complications

• Target organ diseases occur most frequently in the
• Heart Brain Peripheral vasculature Kidney, which preserves blood flow to heart and brain Eyes

Hypertension Complications

• Hypertensive heart disease
• Coronary artery disease
• Left ventricular hypertrophy, with thickening of the muscle
• Heart failure

Hypertension Collaborative Care

• Overall goals: Control blood pressure Reduce cardiovascular disease risk factors
• Drug therapy: primary mechanism of action of drugs to treat hypertension Reduce systemic vascular resistance Reduce volume of circulating blood

Antihypertensive Drugs

• The categories of drugs include:
• Diuretics
• Adrenergic drugs
• Angiotensin converting enzyme (ACE) inhibitors
• Angiotensin II receptor blockers (ARBs)
• Calcium channel blockers (CCBs)
• Direct renin inhibitors
• Vasodilators

Diuretics

• Decrease plasma and extracellular fluid volumes
• Results in: Decreased preload Decreased cardiac output Decreased total peripheral resistance
• Overall effect: Decreased workload of the heart, and decreased blood pressure

Thiazide Diuretics

• Prototype: Hydrochlorothiazide
• First-line treatment for hypertension
• Mechanism of Action: Site of action on distal convoluted tubule of the kidney Inhibits the reabsorption of sodium, potassium, and chloride Results in osmotic water loss Directly relaxes the small blood vessels which reduces peripheral vascular resistance (afterload)
• Indications for Use: Heart failure Hypertension Edema Hypercalciuria Diabetes insipidus
• Contraindications: Drug Allergy Anuria Renal failure

Thiazide Diuretics Adverse Effects

• CNS: Dizziness, headache, blurred vision, paresthesia
• GI: Anorexia, nausea, vomiting, diarrhea, pancreatitis, cholecystitis
• GU: Decreased libido and sexual activity
• Hematologic: Jaundice, leukopenia, purpura, thrombocytopenia
• Integumentary: Urticaria, photosensitivity
• Metabolic: Hypokalemia, glycosuria, hyperglycemia, hyperuricemia
• Toxicity: Overdose can result in severe hypokalemia, lethargy, muscle weakness, confusion, and severe hypotension.

Adrenergic Drugs 'Sympathomimetics'

• Bind to adrenergic receptors, but block stimulation of the sympathetic nervous system (SNS)
• Inhibit or lyse sympathetic stimulation
• Alpha-blockers and beta-blockers
• Classified by the type of adrenergic receptor they block Alpha1 and alpha2 receptors regulate cardiac musculature Beta1 and beta2 receptors
• Multiple sub-groups cause drowsiness or sedation
• Centrally acting alpha2 agonists
• Peripherally acting alpha adrenergic blockers
• Beta Blockers

Adrenergic Drugs: Centrally Acting alpha2 agonists

• Prototype: clonidine (Catapres)
• Other Medications: methyldopa (Aldomet)
• Mechanism of Action Stimulate alpha2-adrenergic receptors in the brain Decrease sympathetic outflow from the CNS Decrease norepinephrine production Stimulate alpha2-adrenergic receptors, reducing renin activity in the kidneys Results in decreased blood pressure
• Indications: Hypertension Clonidine is useful for managing withdrawal symptoms in opioid or nicotine-dependent persons Can be used for hypertension in pregnancy (Methyldopa)

Adrenergic Drugs: Centrally Acting alpha2 agonists

• Contraindications: Use cautiously in patients who have had a stroke, recent MI, major depressive disorder, and chronic renal failure
• Adverse Effects/Side Effects Drowsiness and Sedation Dry Mouth Rebound Hypertension
• Nursing Administration Administered by oral, transdermal, and epidural routes Medication is usually administered twice daily; taking a larger dose at bedtime. Transdermal patches are applied every seven days

Adrenergic Drugs Peripherally Acting Alpha₁ Blocker

• doxazosin mesylate (Cardura)
• terazosin (Hytrin)
• Mechanism of Action is to block alpha1-adrenergic receptors that cause vasoconstriction
• This causes both arterial and venous dilation, reducing peripheral vascular resistance and blood pressure
• Results in decreased blood pressure
• Indications: Used to treat hypertension Tamsulosin (Flomax) affects receptors on the prostate gland and bladder, which decreases obstruction of urinary outflow
• Contraindications: Hypotension Angina and renal insufficiency
• Nursing Administration First dose should be given at night Teach safety measures

Alpha-Blockers: Adverse Effects

• Cardiovascular: Palpitations, orthostatic hypotension, chest pain, tachycardia, edema, dysrhythmias, hypotension or bradycardia
• CNS: Dizziness, headache, drowsiness, anxiety, depression, vertigo, weakness, numbness, fatigue
• Gastrointestinal: Nausea, vomiting, diarrhea, constipation, abdominal pain
• Other: Incontinence, nosebleeds, tinnitus, dry mouth, pharyngitis, rhinitis

Adrenergic Drugs Beta-Blockers

• Work to directly inhibit the effect of stress hormones on the heart
• Block stimulation of beta receptors in the SNS
• Compete with norepinephrine and epinephrine
• Can be selective or nonselective
• Nonselective beta-blockers block both beta₁ and beta2 receptors
• Beta1 receptors are primarily located on the heart
• Beta-blockers selective for these receptors are called cardioselective beta-blockers
• Beta2 receptors are located primarily on smooth muscle of bronchio and blood vessels
• Reduce BP by lowering heart rate
• Cause reduced secretion of renin
• Long-term use causes reduced peripheral vascular resistance

Cardioselctive Beta Blockers

• Reduce SNS stimulation of the heart
• Decrease heart rate
• Prolong SA node recovery
• Slow conduction rate through the AV node
• Decrease myocardial contractility, thus reducing myocardial oxygen demand

Non-Selective Beta Blockers

• Cause same effects on heart as cardio selective beta-blockers
• Can constrict bronchioles, which can result in narrowing of airways and shortness of breath
• Can produce vasoconstriction of blood vessels through smooth muscle
• Reduce heart rate owing to B1-blockade

Beta Blocker Indications

• Angina, as it decreases demand for myocardial oxygen
• Cardioprotective, as it inhibits stimulation from circulating catecholamines
• Post MI administration as it reduces risk of post MI cardiac arrest
• Dysrhythmias
• Migraine headaches
• Antihypertensive
• Heart failure
• Glaucoma (topical use)

Beta-Blockers: Examples

• carvedilol (Coreg)
• labetalol (Normodyne)
• metoprolol (Lopressor)
• atenolol (Tenormin)
• esmolol (Brevibloc)
• propranolol (Inderal)

Adverse Effects: Beta-Blockers

• Blood Adverse Effect: Thrombocytopenia
• Cardiovascular Adverse Effect: AV (heart)block, bradycardia, heart failure, peripheral vascular insufficiency due to slow heart rate CNS Adverse Effects: Dizziness, mental depression, decreased excitability, lethargy, hallucinations, unusual dreams
• Gastrointestinal Adverse Effect: Nausea, dry mouth, vomiting, diarrhea, cramps, ischemic colitis
• Other Adverse Effect: Impotence, rash, alopecia, bronchospasm

Beta-Blocking Drugs: Nursing Implications

• Rebound hypertension or chest pain may occur if this medication is discontinued abruptly
• Instruct patients to notify their physician if they become ill and unable to take medication
• Inform patients that they may notice a decrease in tolerance for exercise (dizziness and fainting may occur with increased activity), and have patients notify the physician if these problems occur
• Inform patients to report the following to their physician: Weight gain of more than 2 pounds in 1 day or 5 pounds in 1 week, due to fluid shifting Edema of the feet or ankles Shortness of breath Excessive fatigue or weakness Syncope or dizziness

Adrenergic Drugs: Summary of Adverse Effects

• High incidence of orthostatic hypotension
• Most common: Dry mouth Drowsiness, sedation (CNS effect) Constipation
• Other: Headaches Sleep disturbances Nausea Rash indicating allergy Cardiac disturbances (palpitations)

Adrenergic-Blocking Drugs: Nursing Implications

• Assess for allergies and history of COPD, hypotension, cardiac dysrhythmias, bradycardia, or heart failure Any preexisting condition that might be exacerbated by the use of these drugs might be a contraindication to their use
• Alpha-blockers may precipitate hypotension
• Beta-blockers may precipitate Bradycardia Hypotension Heart block Heart failure Bronchoconstriction

Adrenergic-Blocking Drugs: Nursing Implications

• Avoid over-the-counter medications because of possible interactions
• Possible drug interactions may occur with: Antacids (aluminum hydroxide type) Antimuscarinics/anticholinergics Diuretics and cardiovascular drugs Neuromuscular blocking drugs Oral hypoglycemic drugs
• Teach patients to change positions slowly to prevent or minimize postural hypotension
• Instruct patients to avoid stimulants such as caffeine (excessive irritability)
• Instruct patients to avoid alcohol ingestion and hazardous activities until blood levels become stable
• Instruct patients to notify their physician if palpitations, dyspnea, nausea, or vomiting occurs
• Monitor for adverse effects
• Monitor for therapeutic effects by measuring BP & HR

Adrenergic-Blocking Drugs: Nursing Implications

• Teach patients to change positions slowly to prevent or minimize postural hypotension
• Instruct patients to avoid stimulants to avoid excessive irritability
• Instruct patients to avoid alcohol ingestion and hazardous activities until blood levels become stable
• Instruct patients to notify their physician if palpitations, dyspnea, nausea, or vomiting occurs
• Monitor for adverse effects
• Monitor for therapeutic effects Monitor BP & HR

Angiotensin Converting Enzymes ACE Inhibitors

• Large group of drugs
• Often used as first-line drugs for heart failure and hypertension
• May be combined with a thiazide diuretic or calcium channel blocker captopril (Capoten) - very short half life enalapril (Vasotec) lisinopril (Prinivil and Zestril)
• Blocks angiotensin-converting enzyme, thus preventing the formation of angiotensin II The conversion of angiotensin I to angiotensin II prevents its activity
• Prevent the breakdown of the vasodilating substance, bradykinin
• Results in decreased systemic vascular resistance (afterload), vasodilation
• Therefore decreased blood pressure

ACE Inhibitors Indications and Special Considerations

• Hypertension
• Heart failure
• Alone or in combination with diuretics or other drugs
• Special considerations: Slow progression of left ventricular hypertrophy after MI cardioprotective Renal protective effects in patients with diabetes, extends life of Kidneys Drugs of choice for Heart failure, hypertensive or diabetic patients

ACE Inhibitors: Adverse Effects

• Fatigue
• Dizziness
• Headache
• Mood changes
• Impaired taste
• Possible hyperkalemia!
• Dry, nonproductive cough, which reverses when therapy is stopped
• Angioedema: rare but potentially fatal

ACE Inhibitors Nursing Administration

• Administered orally, except for enalaprilat (Vasotec IV)
• Ace inhibitors may be combined with hydrochlorothiazide
• Notify providers if cough, rash, and/or signs of infection occur
• First dose orthostatic hypotension may occur
• Monitor potassium levels

Angiotensin II Receptor Blockers (ARBS)

• Newer class of drug
• Well tolerated
• Does not cause a dry cough
• Examples of ARBS include: losartan (Cozaar, Hyzaar) valsartan (Diovan) irbesartan (Avapro) Does not preserve kidneys or heart
• Mechanism of Action: Block vasoconstriction and release of aldosterone
• Indications: Hypertension Stroke Prevention Adjunctive drugs for the treatment of HF May be used alone or with other drugs such as diuretics Used primarily in patients who cannot tolerate ACE inhibitors

Angiotensin II Receptor Blockers

• May cause: Upper respiratory infections Headache Dizziness Inability to sleep Diarrhea Dyspnea Heartburn Nasal congestion Back pain Fatigue Hyperkalemia less likely to occur
• Administration Orally administered May be combined with hydrochlorothiazide Can be taken with or without food

Calcium Channel Blockers

• Some medications include: verapamil (Calan) diltiazem (Cardizem) Nifedipine (Aldat) Amlodipine (Norvasc Felodipine (Plendil) Nicardipine (Cardene)
• Mechanism of Action Smooth muscle relaxation by blocking the binding of calcium to its receptors, preventing muscle contraction
• Decreased: Peripheral smooth muscle tone Systemic vascular resistance Blood pressure
• Indications Hypertension Dysrhythmias Angina Migraine headaches Raynaud's disease
• Adverse Effects Cardiovascular: Hypotension, palpitations, tachycardia Gastrointestinal: Constipation and nausea Other: rash, flushing, peripheral edema
• Nursing Administration Do not chew or crush extended release tablets IV administration of verapamil should be over 2 to 3 minutes Monitor blood pressure, and chest pain

Direct Renin Inhibitors

• aliskiren (Tekturna)
• Mechanism of action: Binds with renin to inhibit production of angiotensin I, thus decreasing production of both angiotensin II and aldosterone.
• Indications: Hypertension
• Adverse Effects: Allergic reaction Hyperkalemia Diarrhea
• Contraindications: Pregnancy risk during 2 and 3 trimesters
• Nursing Considerations: High fat meals interfere with absorption May be taken alone or in combination with other medications

Vasodilators: Indications

• Treatment of hypertension
• May be used in combination with other drugs
• hydralazine HCI (Apresoline)
• minoxidil (Loniten)
• sodium nitroprusside (Nipride, Nitropress)
• Sodium nitroprusside and intravenous diazoxide are reserved for the management of hypertensive emergencies

Vasodilators: Mechanism of Action

• Directly relax arteriolar and/or venous smooth muscle
• Results in: Decreased systemic vascular response Decreased afterload Peripheral vasodilation

Vasodilators Contraindications

• Drug Allergy
• Hypotension
• Cerebral edema / head injury
• Acute MI
• Coronary Artery Disease
• Heart Failure

Vasodilators: Adverse Effects

• Associated with hydralazine
• Dizziness
• Headache
• Anxiety
• Tachycardia
• Nausea/vomiting
• Diarrhea
• Anemia
• Dyspnea
• Edema
• Nasal congestion
• Associated with sodium nitroprusside
• Bradycardia
• Hypotension
• Delirium
• Possible cyanide toxicity (rare)

Vasodilator Toxicity

• Main symptom: Hypotension
• Treatment: Trendelenburg position Supportive and symptomatic treatment IV fluids Sympathomimetics dopamine and norepinephrine usage to increase BP

Social Determinants of Health (SDOH)

• Low education, low SES
• Poverty
• Poor neighborhoods
• Diet high in processed foods,
• Stressful environments
• Alcohol use, smoking, lack of physical activity
• 36% of adults in Monroe County have HTN
• 14605 is the poorest zip code in Rochester

Medication Costs

• Metropolol (generic) - $5 per month
• Hydrochlorothiazide - $17 per month
• Captopril - $23 per month
• Verapamil - $10 per month

Nursing Implications

• Before beginning therapy, obtain a thorough health history and head-to-toe physical examination
• Assess for contraindications to specific antihypertensive drugs
• Assess for conditions that require cautious use of these drugs
• Educate patients about the importance of not missing a dose and taking the medications exactly as prescribed
• Instruct patients to check with their physician for instructions on what to do if a dose is missed; patients should never double up on doses if a dose is missed
• Monitor BP during therapy; instruct patients to keep a journal of regular BP checks

Nursing Implications Continued

• Instruct patients that these drugs should not be stopped abruptly because this may cause a rebound hypertensive crisis, and perhaps lead to stroke
• Oral forms should be given with meals so that absorption is more gradual and effective
• Administer IV forms with extreme caution, and use an IV pump
• Instruct patients to avoid smoking and eating foods high in sodium
• Encourage supervised exercise

Nursing Implications Continued Again

• Teach patients to change positions slowly to avoid syncope from postural hypotension
• Instruct patients to report unusual shortness of breath; difficulty breathing; swelling of the feet, ankles, face, or around the eyes; weight gain or loss; chest pain; palpitations; or excessive fatigue
• Male patients who take these drugs may not be aware that impotence is an expected effect, and this may influence compliance with drug therapy
• If patients are experiencing serious adverse effects, or if they believe the dose or medication needs to be changed, they should contact their physician immediately

Nursing Implications One Last Time

• Hot tubs, showers, or baths; hot weather; prolonged sitting or standing; physical exercise; and alcohol ingestion may aggravate low blood pressure, leading to fainting and injury; patients should sit or lie down until symptoms subside
• Patients should not take any other medications, including over-the-counter drugs, without first getting the approval of their physician
• Educate patients about lifestyle changes that may be needed Weight loss Stress management Supervised exercise Dietary measures
• Monitor for adverse effects Dizziness Orthostatic hypotension Fatigue Toxic effects
• Monitor for therapeutic effects Blood pressure should be maintained at less than 130/90 mm Hg If a patient with hypertension also has diabetes or renal disease, the BP goal is less than 130/80 mm Hg (JNC-7)

Gerontologic Considerations

• Age alters the cardiovascular response to physical and emotional stress.
• Heart valves become thick and stiff.
• Frequent need for pacemakers
• Less sensitive to ẞ-adrenergic agonist drugs
• Increase in SBP; decrease or no change in DBP

Cultural Considerations

• Beta-blockers and ACE inhibitors have been found to be more effective in white patients than in African American patients
• CCBs and diuretics have been shown to be more effective in African American patients than in white patients