Comprehensive Cardiac Nursing and Advanced Rhythm Analysis

Cardiac Anatomy and Physiology Overview

• Unique Blood Supply: The heart is one of the few organs where the blood supply sits on the outside of the organ itself. Major arteries and veins supplying circulation are located on the heart muscle's exterior.

• Heart Rotation and Contraction Cycles:

  • Similar to hand veins engorging when hanging down and flattening when making a fist, heart vessels are compressed during contraction (systole) and fill between beats (diastole).

  • Naturally, the heart is designed for this cycle. However, extreme heart rates (e.g., $150\text{--}160\,bpm$) prevent arteries from filling adequately with oxygen-rich blood.

• Clincial Implications of High Heart Rates:

  • Patients in Atrial Fibrillation (A-fib) with rapid ventricular rates may experience chest pain because the heart muscle is deprived of oxygen (ischemia) due to insufficient filling time.

  • Troponin Elevation: Stress from high heart rates can cause a slightly elevated troponin level, as troponin is released whenever the heart muscle is damaged, stressed, or deprived of oxygen.

• Blood Flow Pathway:

  • Oxygen-rich blood leaves the left ventricle through the aorta.

  • The coronary arteries are the first to branch off the aorta; the heart feeds itself first before blood reaches the arms, neck, brain, and the rest of the body.

• Venous Return:

  • Superior Vena Cava: Drains blood from the head, neck, and shoulders back into the heart.

  • Inferior Vena Cava: Returns blood from the lower part of the body.

  • Jugular Venous Distension (JVD): Occurs in congestive heart failure when the heart is fluid-overloaded, preventing proper drainage from the superior vena cava; blood builds up in the neck and shoulder area.

Structural Layers of the Heart

• Pericardium: A protective, fibrous sac/membrane surrounding the heart. It prevents friction irritation from lungs and other chest organs as the heart beats.

• Endocardium: The innermost lining of the heart's chambers. It is a very smooth muscle layer designed to prevent clot formation and debris accumulation.

  • Endocarditis: Inflammation of this lining, often seen in IV drug users or patients with untreated rheumatic fever (strep infection).

• Myocardium: The thickest, middle layer; the "workhorse" muscle responsible for contraction and relaxation (the heartbeat).

  • Myocarditis: Inflammation of the myocardium can be caused by viral infections (like the flu), autoimmune disorders, or trauma.

• Epicardium: The outer protective, fibrous coating of the heart muscle.

Cardiovascular Laboratory Testing and Lipids

• Lipid Profile Components:

  • HDL (High-Density Lipoproteins): Often called "happy cholesterol." These molecules are larger and less likely to wedge into blood vessel nooks and crannies to form plaque.

  • LDL (Low-Density Lipoproteins): This is primarily responsible for plaque formation in arteries.

  • Total Cholesterol Target: Should be less than $200\,mg/dL$.

  • Triglycerides: A combination of cholesterol and sugar molecules; often higher in uncontrolled diabetics. The normal fasting range should be below $150\,mg/dL$.

• Testing Requirements: Patients should fast for at least $12\,hours$ for a true reading. Random draws must be documented so the physician can interpret the values correctly (e.g., levels are significantly higher after a meal).

• Pharmacological Treatment (Statins):

  • Common meds: Atorvastatin (Lipitor) and Rosuvastatin (Crestor). Atorvastatin is the only long-acting statin.

  • Administration: Most are taken in the evening because the body/liver synthesizes the majority of its cholesterol during sleep.

  • Black Box Warning: Patients must report severe muscle cramping or weakness immediately. Statins can trigger the breakdown of skeletal muscle tissue (rhabdomyolysis). This is often dose-dependent.

  • Ezetimibe (Zetia): Often used in conjunction with statins. It is effective at balancing the ratio between HDL and LDL.

Cardiac Biomarkers and Enzymes

• Troponin (Troponin I):

  • The primary biochemical factor released when the heart is damaged or stressed. A higher number indicates worse damage.

  • It is the standard test for identifying myocardial infarctions (heart attacks).

  • Chronic Elevation: Patients with chronic kidney disease or chronic heart failure may have a mildly elevated baseline. Clinicians must trend troponin levels every $4\,hours$ to look for significant increases.

  • Elevation occurs within $1\text{--}2\,hours$ of damage.

• CK-MB (Creatine Kinase-MB):

  • An older enzyme test released when any muscle is damaged, but specific to the heart.

  • It takes up to $16\,hours$ for an elevation to appear, making it less efficient than Troponin.

• BNP (Brain Natriuretic Peptide):

  • Secreted primarily by the right atria in response to stretching caused by fluid overload.

  • Normal range: Below $100\,pg/mL$. Levels above $5,000\,pg/mL$ indicate severe overload (patient may sound like they are drowning).

  • Physiology: The BNP signals the brain (pituitary) to tell the kidneys to increase urination. This works in healthy people, but in heart failure, the kidneys do not receive enough blood flow to respond, leading to a vicious cycle of fluid retention and heart stress.

Diagnostic Procedures

• TTE (Transthoracic Echocardiogram):

  • A non-invasive ultrasound of the heart to look at the structure and valves.

  • Ejection Fraction (EF): Measures the percentage of blood pumped with each beat. Normal (athletes) is around $85\%$. Heart failure diagnosis occurs when the EF drops below $50\%$.

• TEE (Transesophageal Echocardiogram):

  • A probe is inserted into the esophagus to get a closer look at the right side of the heart and valves.

  • Nursing Considerations: Patient must be NPO (nothing by mouth) for at least $6\,hours$ to prevent aspiration. The nurse must check the gag reflex after the procedure before the patient is allowed to eat or drink.

• Stress Test:

  • Monitors heart function (rhythm and symptoms like chest pain) under exertion.

  • Methods: Treadmill (elevating heart rate to approximately $120\,bpm$) or a pharmacological stress test (using IV meds for patients who cannot walk).

  • Prep: No caffeine; check orders regarding whether to hold heart medications (e.g., metoprolol).

• EKG (Electrocardiogram):

  • The priority intervention for patients presenting with chest pain. National guidelines require an EKG within $10\,minutes$ of arrival with cardiac symptoms.

  • Lead Placement:

    • 12-lead EKG uses $10\,cables$.

    • V1 (4th intercostal space, right of sternum).

    • V2 (4th intercostal space, left of sternum).

    • V4 (5th intercostal space, mid-clavicular).

    • V6 (5th intercostal space, mid-axillary).

    • V3 and V5 go in between.

    • Arm/Leg leads: Avoid bony areas; place on muscle for better conduction.

Angina and Chest Pain Management

• Stable Angina: Predictable chest pain caused by exertion (e.g., climbing stairs) that goes away with rest.

• Unstable Angina: Chest pain that occurs even at rest. This is ominous and indicates significant blockage.

• Variant (Prinzmetal) Angina: Often seen in younger, athletic people; caused by coronary artery vasospasms. Can mimic both stable and unstable angina. Treated with Calcium Channel Blockers (e.g., Diltiazem or Amlodipine).

• Nitroglycerin Protocol:

  • Purpose: Dilate coronary arteries to increase blood flow.

  • Assessment: Before administration, assess blood pressure (BP) and pain level ($0\text{--}10$ scale). Do not give if systolic BP is under $100\,mmHg$.

  • Administration: Sublingual (under the tongue) for fast absorption. Take $1\,tablet$ every $5\,minutes$ for up to $3\,doses$.

  • Patient Education: Keep tablets in the original dark glass vial (sensitive to light). Do not transfer to plastic. Do not take all three pills at once.

  • Nursing Safety: Ensure the patient has an IV established, as nitroglycerin can drastically drop blood pressure.

• Isosorbide Dinitrate (Imdur): A long-acting nitrate for patients with unstable angina who are not candidates for surgery.

Myocardial Infarction: STEMI vs. NSTEMI

• STEMI (ST-Elevation MI): Indicates a complete or significant blockage causing heart muscle death and rhythm changes (bunny ears on EKG). This is an emergency requiring the cath lab within $60\,minutes$.

• NSTEMI (Non-ST-Elevation MI): Symptoms of a heart attack and elevated troponins but minimal or no EKG changes. This indicates decreased blood flow that is not yet affecting global heart function; cath lab can usually wait $1\text{--}2\,days$.

Cardiac Catheterization (Cath Lab)

• Approaches:

  • Radial Artery (Wrist): Preferred due to fewer bleeding complications and increased patient comfort. Use of a TR Band (clear pressure band) involves releasing air gradually over several hours.

  • Femoral Artery (Groin): Used if radial access fails. Patient must remain flat on their back for at least $6\,hours$ post-procedure with the leg straight.

• Interventions: Balloon angioplasty (pushing plaque back) and stent deployment (mesh tube to keep the artery open).

  • Stents: Often drug-eluting (containing chemicals like Tacrolimus/Prograf) to prevent tissue scarring. Patients should carry a medical card for MRI safety.

• Post-Cath Nursing Assessment:

  • Neurovascular Checks: Most distal points (fingers for radial, toes for femoral). Check pulses, color, temperature, and sensation (numbness/tingling).

  • Bleeding: Monitor site for hematoma or active bleeding.

Rhythm Interpretation Fundamentals

• P Wave: Atrial depolarization (contraction). Triggered by the SA node. Should be followed by a QRS.

• PR Interval: Time from atrial start to ventricle start. Normal is no more than $0.2\,seconds$ (one big box on grid).

• QRS Complex: Ventricular depolarization (contraction). Normal is no more than $0.12\,seconds$ (three tiny boxes). A wide QRS (> 0.12) indicates a bundle branch block.

• T Wave: Ventricular repolarization (rest/resting). Should return to baseline. If it pulls above baseline, it indicates ST elevation.

• Lethal/Urgent Rhythms:

  • Sinus Bradycardia: Normal complex but rate < 60\,bpm.

  • V-Tach (Ventricular Tachycardia): Rapid ventricular rate, wide QRS, no P waves. Lethal; requires CPR and defibrillation if pulseless.

  • A-Fib (Atrial Fibrillation): Irregularly irregular, no distinct P waves. Atria quiver. Can have RVR (Rapid Ventricular Response).

  • A-Flutter: "Sawtooth" pattern of regular P waves (e.g., 2:1 or 4:1 ratio to QRS).

  • V-Fib (Ventricular Fibrillation): Quivering ventricles, no pulse, squiggly baseline. Emergency.

Pacemakers and Internal Defibrillators

• Pacemaker Types:

  • Atrial: Spike before the P wave.

  • Ventricular: Spike before a wide QRS. Most common.

  • Dual Chamber: Spikes before both P and QRS.

• Malfunctions:

  • Failure to Capture: Pacemaker sends a spike, but the heart does not contract.

  • Failure to Sense: Pacemaker does not recognize the patient's own beats and shocks randomly; very dangerous if it hits the T wave.

• Nursing Care & Education:

  • Post-Op: Arm in a sling for $1\text{--}2\,weeks$ to prevent lead displacement; no heavy lifting; monitor for swelling/pocket of blood.

  • Safety: Keep cell phones on the opposite side of the generator. Carry the medical ID card.

  • ICD (Internal Cardiac Defibrillator): Used if EF is < 20\%. If it fires (fells like a horse kick), the patient must go to the ER immediately.

  • Turning Off: A large circular magnet placed over the generator will temporarily disable the device.

Questions & Discussion

• Student Question: Are the zeros in the Gradebook for the Sim Lab permanent?

• Answer: No. If you didn't have Sim Lab that week, a zero displays until the instructor marks it as "exempt," which switches the grade back.

• Student Question: Do we have anything due for lab this week?

• Answer: Only if it is your scheduled Sim Lab day; then you have a pre-assignment and a post-assignment on Mondays.

• Student Question: Regarding the ATI cardiovascular module, what is required for the grade?

• Answer: You must complete the entire module, including the case and the post-test. A missing percentage on the report means something, like the EHR component, wasn't clicked/completed.

• Student Question: What is the normal value for triglycerides?

• Answer: Fasting normal should be below $150\,mg/dL$.

• Student Question: Why is the EKG called a 12-lead if there are only 10 cables?

• Answer: The 10 cables look at 10 areas, and the machine prints out 12 different views (rhythms), including long rhythm strips at the bottom.

• Student Question: What happens if the pacemaker is set at one rate and the heart is slower?

• Answer: If the pacer is set at $70\,bpm$ but the patient's pulse is $60\,bpm$, there is a malfunction; the pacer should have kicked in once the rate dropped below the setting.

• Student Question: Can we get shocked by an internal defibrillator if we touch the patient?

• Answer: No, but the patient will experience a significant physical jerk.