Cardiology notes

Cardiology Introduction

• Definition: Cardiology is the branch of medicine that focuses on the treatment of disorders related to the heart and circulatory system.

• Specialists: Medical doctors who specialize in diagnosing and treating heart conditions are called cardiologists.

Common Conditions

• Hypertension:
    - Definition: High blood pressure.
    - Normal Range: Normal resting blood pressure is $120/80 ext{ mmHg}$.
    - Indication: Consistently elevated blood pressure readings may indicate hypertension.

• Heart Failure:
    - Definition: The heart cannot pump blood effectively.
    - Symptoms: Results in shortness of breath and fatigue.

• Arrhythmia:
    - Definition: An abnormal heart rhythm.
    - Example: Includes conditions like atrial fibrillation.

• Coronary Artery Disease (CAD):
    - Definition: Narrowing or blockage of arteries in the heart.

• Angina:
    - Definition: Chest pain caused by reduced blood flow to the heart muscle.

• Myocardial Infarction:
    - Common Name: Heart attack.
    - Definition: Occurs when blood flow to a part of the heart is blocked, resulting in tissue damage.

Pharmacotherapy

• Classes of Medications:
    - Angiotensin-converting enzyme inhibitors (ACE inhibitors)
    - Angiotensin receptor blockers (ARBs)
    - Beta-blockers
    - Calcium channel blockers (CCBs)
    - Diuretics
    - Blood thinners
    - Alpha-blockers
    - Peripheral vasodilators
    - Nitrites

Angiotensin-Converting Enzyme Inhibitors (ACE Inhibitors)

• Generic Names & Brand Names:
    - Lisinopril: Zestril; Prinivil
    - Benazepril: Lotensin
    - Ramipril: Altace
    - Enalapril: Vasotec

• Abbreviation: ACE Inhibitors; ACE-Is

• Mechanism of Action: ACE inhibitors block an enzyme that activates angiotensin, a hormone that regulates blood pressure.

• Common Suffix: -pril

• Adverse Reaction:
    - Description: ACE-Inhibitor induced cough.
    - Management: Patients who experience this side effect will need to be switched to a different class of medication, usually replacing the ACE-I with an angiotensin receptor blocker.

• Contraindication: ACE inhibitors are contraindicated in pregnancy.

Angiotensin Receptor Blockers (ARBs)

• Generic Names & Brand Names:
    - Losartan: Cozaar
    - Olmesartan: Benicar
    - Irbesartan: Avapro
    - Valsartan: Diovan

• Abbreviation: ARB

• Mechanism of Action: ARBs inhibit the action of angiotensin by blocking the receptors it normally binds to, producing a similar effect to ACE inhibitors.

• Common Suffix: -sartan

• Contraindication: ARBs are contraindicated in pregnancy.

• Adverse Reaction: Unlike ACE inhibitors, ARBs do not cause a cough as an adverse reaction.

Beta-Blockers

• Generic Names & Brand Names:
    - Metoprolol Tartrate: Lopressor
    - Metoprolol Succinate: Toprol XL
    - Carvedilol: Coreg
    - Atenolol: Tenormin
    - Labetalol: Trandate
    - Propranolol: Inderal

• Mechanism of Action: Beta-blockers lower the heart rate, leading to decreased blood pressure.

• Common Suffix: -lol

• Indications: Useful in treating many heart conditions, including hypertension, heart failure, and arrhythmias.

• Formulations of Metoprolol:
    - Metoprolol Tartrate (Lopressor): Immediate-release tablets, typically dosed twice daily.
    - Metoprolol Succinate (Toprol XL): Extended-release tablets, typically dosed once daily.

• Drug-Disease Interaction:
    - Condition: Asthma
    - Effects: Beta-blockers constrict airways, causing exacerbations in patients with asthma. Therefore, they are generally avoided in asthmatic patients.

Calcium Channel Blockers (CCBs)

• Generic Names & Brand Names:
    - Amlodipine: Norvasc
    - Nifedipine: Procardia; Adalat
    - Diltiazem: Cardizem
    - Verapamil: Calan

• Common Abbreviation: CCB

• Mechanism of Action: Calcium channel blockers block calcium channels in the heart muscle, leading to cardiac muscle relaxation and blood vessel dilation, which results in lower blood pressure.

• Types:
    - Dihydropyridine: End with the suffix -pine.
    - Non-dihydropyridine: Do not have a common suffix.

Diuretics

• Definition: Commonly referred to as “water pills.”

• Mechanism of Action: Diuretics direct the kidneys to increase the amount of water excreted in urine, which lowers blood volume and consequently decreases blood pressure.

• Counseling Point: Patients should expect increased urination and should take diuretics in the morning to decrease nighttime urination and sleep disturbances.

• Types of Diuretics:
    - Thiazide diuretics
    - Loop diuretics
    - Potassium-sparing diuretics

Thiazide Diuretics

• Generic Names & Brand Names:
    - Hydrochlorothiazide: Microzide
    - Chlorthalidone: Thalitone
    - Metolazone: Zaroxolyn

• Mechanism of Action: Thiazide diuretics increase the excretion of water along with potassium and sodium.

• Adverse Drug Reactions:
    - Hypokalemia: Decreased potassium.
    - Hyponatremia: Decreased sodium.
    - Photo-sensitivity: Increased sensitivity to sunlight.

• Sodium Dietary Note: Most patients get enough sodium in their diet, so hyponatremia is typically not an issue.

• Potassium Dietary Note: Many patients may need to supplement their diet with potassium chloride due to low dietary potassium.

• Abbreviation: Hydrochlorothiazide is commonly abbreviated as HCTZ.

• Combination Medications: Hydrochlorothiazide is often combined with blood pressure medications from other classes to make combination pills, e.g.:
    - Lisinopril / HCTZ
    - Valsartan / HCTZ
    - Triamterene / HCTZ

Loop Diuretics

• Generic Names & Brand Names:
    - Furosemide: Lasix
    - Bumetanide: Bumex
    - Torsemide: Demadex

• Mechanism of Action: Loop diuretics increase excretion of water by excreting potassium.

• Common Suffix: -ide

• Adverse Reactions:
    - Hypokalemia: Decreased potassium.
    - Potassium Supplementation: Many patients may need to supplement with potassium chloride.

Potassium-Sparing Diuretics

• Generic Names & Brand Names:
    - Spironolactone: Aldactone
    - Triamterene / HCTZ: Dyazide

• Mechanism of Action: Potassium-sparing diuretics increase water excretion without wasting potassium.

• Adverse Reaction: May cause increased potassium (hyperkalemia).

• Counseling Point: Patients should avoid salt substitutes which contain potassium; using them with potassium-sparing diuretics increases the risk of hyperkalemia.

Electrolytes

• Supplement:
    - Potassium Chloride: Available under various brand names (e.g., Klor-Con; K-Dur; K-Tab).

• Overview:
    - Thiazide and loop diuretics increase potassium excretion into urine, potentially leading to low potassium.
    - Patients on potassium-sparing diuretics do not need potassium supplementation.
    - Potassium chloride is available in tablet, capsule, and oral solution forms; oral solution should be diluted in water before taking.

• Dosage: Dosed in milliequivalents (mEq), not milligrams.
    - Example: Potassium Chloride 20 mEq PO QD.

• Symbol for Potassium: “K” is the chemical symbol for potassium, explaining its use in various potassium chloride brand names.

Alpha-Blockers

• Generic Names & Brand Names:
    - Doxazosin: Cardura (HTN / BPH)
    - Terazosin: Hytrin (HTN / BPH)
    - Prazosin: Minipress (HTN)
    - Tamsulosin: Flomax (BPH)

• Indications: Alpha-blockers are used for treating high blood pressure and benign prostatic hyperplasia (BPH).

• Notable Point: Tamsulosin is not indicated for hypertension but is included for comparison.

• Adverse Reactions:
    - Dizziness, orthostatic hypotension.

• Counseling Point: Patients may experience blood pressure drops when transitioning positions (from sitting to standing), potentially causing dizziness. Advise caution during such transitions.

Peripheral Vasodilators

• Generic Names & Brand Names:
    - Hydralazine: Apresoline.

• Mechanism of Action: Peripheral vasodilators dilate blood vessels, resulting in lowered blood pressure.

• Caution: Hydralazine is a look-alike/sound-alike drug; be careful when dispensing.

Alpha Agonists

• Generic Names & Brand Names:
    - Clonidine: Catapress

• Mechanism of Action: Alpha agonists affect neurotransmitters in the brain to lower blood pressure.

• Other Indication: Also used in the treatment of Attention Deficit Hyperactivity Disorder (ADHD).

Blood Thinners

• Generic Names & Brand Names:
    - Aspirin: Various (Salicylate)
    - Clopidogrel: Plavix (Antiplatelet)
    - Ticagrelor: Brilinta (Antiplatelet)
    - Warfarin: Coumadin (Anticoagulant)
    - Apixaban: Eliquis (Anticoagulant)
    - Rivaroxaban: Xarelto (Anticoagulant)
    - Dabigatran: Pradaxa (Anticoagulant)
    - Enoxaparin: Lovenox (Anticoagulant)

• Definition: Blood thinners are medications that prevent blood clots from forming inside blood vessels.

• Indication: Useful for patients with health conditions like arrhythmias and certain procedures that increase clotting risk.

• Adverse Reactions: Increased risk of bleeding.
    - Counseling Point: Patients should contact their physician if noticing abnormal or severe bleeding (e.g., nosebleeds, bleeding gums, easy bruising).

• Combination Use: Blood thinners from different classes can be used together with caution regarding potential interactions.

• Administration:
    - Enoxaparin: Administered via subcutaneous injection; all other agents are oral.

Warfarin Clinical Pearls

• Narrow Therapeutic Index Drug:
    - Minor changes in dose can lead to significant changes in drug blood levels.

• Monitoring: Requires frequent blood work to ensure blood levels are appropriate. The test used is called INR.
    - Adjustments: If the INR is too high, the warfarin dose may be reduced; if too low, it may be increased.

• Available Doses:
    - Available in tablets of 1mg, 2mg, 2.5mg, 3mg, 4mg, 5mg, 6mg, 7.5mg, and 10mg.
    - Color-Coding: Tablets are color-coded for safety, e.g., a 5mg tablet is always peach regardless of manufacturer.

• Dosing Variability: Doses may change depending on the day of the week, e.g.:
    - Take 5mg daily Monday – Saturday; 6mg on Sundays.
    - Take 3mg on Tuesday, Thursday, and Saturday; 4mg on all other days.

• Reversal Agent: Vitamin K (phytonadione) can reverse the effects of warfarin in cases of overdose or for surgery preparation.
    - Dietary Note: Vitamin K is primarily found in green, leafy vegetables (e.g., kale, spinach, cabbage).
    - Patients are advised to maintain a consistent intake of these vegetables rather than avoiding them entirely.

Nitrates

• Generic Names & Brand Names:
    - Isosorbide / Hydralazine: BiDil
    - Nitroglycerin Sublingual Tablets: Nitro-Quick; Nitro-Stat

• Indication: Nitrates are used to treat or prevent angina (heart pain).

• Mechanism of Action: Nitrates dilate (widen) arteries, increasing blood flow.

• Administration: Sublingual tablets are placed under the tongue and used as needed (PRN) for heart pain.

• Contraindications: Major contraindication includes use with phosphodiesterase-5 inhibitors (PDE-5 inhibitors).
    - Examples: Sildenafil (Viagra); Tadalafil (Cialis).
    - Risk: Both nitrates and PDE-5 inhibitors dilate blood vessels, which can cause severe drops in blood pressure leading to serious complications (e.g., dizziness, fainting, heart attack, stroke).

Digoxin

• Generic Names & Brand Names:
    - Digoxin: Lanoxin; Digitek

• Indications: Used for heart failure and atrial fibrillation.

• Mechanism of Action: Digoxin slows down the heart rate while increasing the force of contraction.

• Narrow Therapeutic Index Drug: Small changes in dose can lead to significant differences in blood concentrations.