Cardiac Testing

Anatomy of the heart and coronary arteries

  • 2 sides separated by septum
    • Right side– pumps deoxygenated blood to lungs
      • Vena Cava:  carries oxygen-poor blood from body to the right side of the heart
      • Pulmonary Artery:  carries oxygen-poor blood from right side of heart
    • Left side– pumps oxygenated blood to the rest of the body
      • Pulmonary veins:  carry oxygen rich-blood from lungs to left side of heart
      • Aorta:  main artery in heart that carries oxygen-rich blood from left side of heart out to the body
        • Coronary arteries are what carry oxygen-rich blood from aorta to heart muscle (heart muscle needs it’s own blood supply to function)
          • The coronary arteries (left CA, right CA, circumflex branch, anterior interventricular artery (either ascending or descending) are what are blocked in the case of an MI
  • 4 chambers & 4 valves connected by various blood vessels
  • S1  (“Lub”)
    • 1st normal heart sound that represents the mitral & tricuspid valves closing at the beginning of systole
    • Ventricular contraction
  • S2 (“Dub”)
    • 2nd normal heart sound
    • Aortic & pulmonary valves closing at beginning of diastole
    • Ventricular relaxation & filling

Cardiac diagnostic procedures:

  • Chest Radiography
    • Usually the 1st diagnostic test done in a cardiac work-up
    • Tells the position & size of heart along with the surrounding anatomy
  • Echocardiogram (ECHO)
    • Initial evaluation tool used following the ausculation of an abnormality
    • Ultrasound–speed at which the sound waves bounce back is determined by the density of the tissue/fluid it comes in contact with
    • Outpatient procedure that’s non-invasive & can be done w/ or w/o contrast
    • Uses of ECHO–pretty much an ECHO is the shit
      • Ventricular dysfunction
      • Identify cardiac thrombus & cardiac tumors
      • Evaluate blood flow through the heart  (flow direction–antegrade & retrograde)
      • Useful in following the progression of the disease over time
      • Evaluate a heart murmur
      • Assess cardiomyopathy
      • Valvular dysfunction (aortic & mitral stenosis, regurgitation & endocarditis)
      • Wall motion abnormalities resulting from ischemia
      • Congenital abnormalities (ventricular or atrial septal defects)
      • To estimate chamber wall thickness & ejection fraction      (the more wall thickness, more likely to have disease)
      • Detect abnormalities of the pericardium (effusions or thickening)
  • Nuclear imaging  (most commonly uses Technetium-99 & Thallium-201 as nuclear agents)
    • Used in combo w/ other cardiac tests
    • Technetium nuclear scanning
      • evaluates blood pool & myocardial perfusion
        • Identifies the damaged part of the myocardium by uptaking the agent into the infarcted area  (hot-spot scanning)
      • Short half-life (6 hours) allows for continual evaluations over a short period of time.
    • Thallium nuclear scanning
      • Analyzes coronary & myocardial perfusion
      • Taken up into the normal myocarium (cold-spot scanning)
      • Can correlate ischemia to anatomic regions & wall motion abnormalities;  useful for atypical chest pain or ambiguous results
      • Longer half-life (73 hours)–good for delayed imaging
  • Exercise Stress Testing
    • Noninvasive test for suspected ischemic heart disease (want to provoke ischemia in a controlled environment)
      • Ischemia detected by patient symptoms, ECG changes &/or hemodynamic changes
    • Provides prognosis info following a heart attack or revascularization (helps in selection of pharmacotherapy)
      • Used as an initial evaluation tool in combo w/ a physical exam & reported symptoms of chest pain or equivalents
    • Usually keep patient on their meds (BB & CCBs may cause patient not to achieve max HR; Nitrates improve patient’s response; digoxin may interfere w/ interpretation of ST-segment changes)
  • Pharmacological stress test
    • Used in patients that don’t want to do an exercise test  (still used in combo w/ ECHO, nuclear imaging, etc)
    • Use either coronary perfusion agents (dipyridamole & adenosine) or by increasing myocardial oxygen demand (dobutamine +/- atropine)
      • Dipyridamole inhibits adenosine cellular uptake leading to an increased [adenosine] in blood & tissues
        • Adenosine is a potent coronary vasodilator & will increase perfusion
        • Used in combo w/ cold spot nuclear imaging to identify areas of ischemia (areas not vasodilated are cold–ischemic)
        • SE of these perfusion agents: HA, dizziness, nausea, chest pain
        • Adenosine’s adverse effects can be alleviated by xanthine compounds (ex. Caffeine) which competitively inhibit adenosine
          • This is why a patient should avoid caffeine for at least 24 hours prior to test
        • Contraindicated in patients w/ history of bronchospasm
      • Dobutamine stress test
        • Dobutamine (10-40mcg/kg/min in 3 minute intervals starting at 10 mcg/kg) is a catecholamine that raises HR & CO thus increasing myocardial oxygen demand
        • Detects ischemia via ECG, ECHO, thallium scanning (Cold spots–admin prior to end of dobutamine infusion)
        • Admin’d & titrated according to target HR (85% of patients calculated max HR–>  HRmax = 220 – age)
          • Target: 85% of HRmax (HRmax = 220 – age)
          • Atropine 0.25 mg/min for up to 4 doses may be used to reach the target HR   (max of 1 mg Atropine)
        • Must record ECG & BP continuously throughout test
        • Get ECHO recordings during the last minute of each dose level & during recovery
        • Meds to discontinue prior to the test:  beta blockers (reverse most adverse effects of test), CCBs, nitrates, avoid caffeine products
        • Discontinue stress test if:  Severe chest pain, extensive new wall motion abnormalities, ST-segment elevation and depression, tachyarrhythmias, symptomatic reductions in blood pressure
  • Coronary Angiography  (aka heart cath)
    • Used to assess coronary vessels & cardiac function   (used either as a diagnostic tool or in acute situations)
    • Contraindications:  recent stroke, old age, severe anemia, severe HTN, active GI bleed
    • Inject dye via catheter into coronary arteries &/or ventricle at the radial, brachial or femoral arteries or veins
    • Left-sided catheterization (coronary angiography & ventriculography):  provides access to the aorta, left ventricle & left atrium
    • Right-sided catherization (cardiac performance):  provides access to the right side of the heart, coronary sinus, pulmonary arteries & pulmonary wedge pressure.
    • Prep:
      • Patient should be NPO after midnight the night before except for oral meds
        • Discontinue warfarin, potentially ASA, clopidogrel (plavix), metformin
      • Patients who need anticoagulant bridge therapy should be given UFH (unfractionated heparin) or LMWH
    • Usually an outpatient procedure except if an immediate intervention is required, poor renal function, contrast allergy
    • Patients are under conscious sedation during the procedure (they are aware & awake)
      • Given either midazolam or another short-acting benzo
    • Patients will frequently develop chest pain &/or vasospasm during introduction & manipulation of the catheters & injection of dye
      • Nitroglycerin, nitroprusside &/or morphine can be given for the chest pain
      • Nitroglycerin (SL or IV) can also be used to prevent vasospasm
    • Heparin products are used to prevent thrombotic complications during the procedure
      • Depending on the nature of the procedure, heparin should be discontinued either immediately or continued for 12-24 hours
        • Heparin admin is based on activated clotting time (ACT)
      • Clopidogrel (plavix) & Aspirin are used before the procedure if the patient is undergoing percutaneous coronary intervention
    • Patient needs to remain still for 6-8 hours following the heart cath to reduce risk of bleeding from cathetar sites (may be discharged the same day or the next morning)
    • The images for the coronary angiography are used to determine the morphology of the lesion & the degree of obstruction
      • The extent of the disease is defined as the number of vessels & which vessels are affected  (used to plan interventions)
  • Ventriculography
    • Provides info about the shape of the heart & global function.  (regional wall motion, filling defects & the presence of mural thrombi)
  • Intravascular Ultrasound
    • Allows for the visualization of questionable coronary lesions (quantitative & qualitative)
    • Small transducer on the tip of a coronary catheter
  • 64-Slice Computed Tomography
    • Used outpatient, in situations where coronary angiography is too invasive
    • Becoming increasingly popular as a primary screening tool b/c it’s less invasive/expensive & is effective in younger population
    • Used determine chamber volume, size & thickness of myocardial wall
    • Can also be used to assess coronary arteries, aortic, cardiac masses & pericardial disease
    • Quality images require patients to hold their breath & have a normal sinus rhythm & a targeted HR of < 65 BPM
      • Beta blockers may be used to reduce the patient’s HR
  • Holter Monitor
    • Continuous or intermittent recording of HR & rhythm
    • Evaluates: arrhythmias, slowest HR, fastest HR, association of symptoms (patient presses a button if symptomatic)
  • Electrophysiology Study
    • Performed similar to a heart cath w/ catheter electrodes inserted inside the heart
    • Used to map electrical circuits when the arrhythmias are difficult to diagnose
    • May be used to induce arrhythmias
    • Most often used on an outpatient basis
    • Don’t use in patients w/ a pacemaker or with poor kidney function

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