Cardiology

• EKG


  3 – 5 big boxes between QRS complexes
• Determining Heart Rate


  • 300
  • 150
  • 100
  • 75
  • 60
  • 50

  
• Cardiac conduction system


  • SA
  • AV
  • His
  • RBB
  • LBB
  • Purkinje Fibers

  
• Normal QRS Axis


  • 30 and +90 degrees
• QRS Axis


  • 0°
  • -90°
  • +180°
• Left Axis Deviation


  • LBBB
  • Ventricular Rhythm

  
• Right Axis Deviation


  • RBBB
  • RVH

  
• Determining Axis


  1. Look at lead I (-) and lead aVF (+)

  2. Normal axis is -30 to +90
• Axis Quick Method


  • First, glance at aVr (should be negative)
  • If leads I and II are both positive, axis is normal
  • If lead II is negative, axis is left
  • If lead I is negative, axis is right
• Step 1: Find the p waves


  1. Are p waves present?

  2. Sinus p waves originate in sinus node and are upright in leads II, III, F
• Step 2: Regular or Irregular


  1. Check distance between QRS complexes (R-R intervals)

  2. Regular

  3. Irregular
• Rhythms based on Steps 1 & 2


  • Sinus rhythm
  • Atrial fibrillation
  • Sinus rhythm with PACs
  • Multifocal atrial tachycardia
  • Mobitz I AV Block (Wenckebach)
  • AV Nodal Reentrant Tachycardia (AVNRT)

  
• QRS Interval


  • Narrow QRS (< 120 ms; 3 small boxes) = His-Purkinje system works, no bundle branch blocks
  • Wide QRS = bundle branch block or ventricular rhythm
• Step 4: Check the intervals

  1. PR (normal < 210 ms; ~5 small boxes; ~1 big box)

  2. QT (normal < 1/2 R-R interval)
• Step 5: ST segments


  • T wave abnormalities (inverted, peaked, flat/U waves)
  • ST depression (subendocardial ischemia)
  • ST elevation (transmural ischemia, STEMI, hyperkalemia, early ischemia)
• PAC and PVC
• Coronary Artery Disease


  • Narrowing of coronary artery caused by atherosclerosis
  • Asymptomatic until ~75% artery lumen occluded
  • Causes chest pain (angina), dyspnea, other symptoms
• Coronary Artery Disease Progression


  • Asymptomatic
  • Stable Angina
  • Unstable Angina
  • NSTEMI
  • STEMI
• Major Risk Factors for CAD


  • Diabetes
  • Chronic kidney disease
  • Hypertension
  • Hyperlipidemia (LDL)
  • Age (M > 45, F > 55)
  • Family History of premature CAD (1° relative, M < 55, F < 65)
  • Smoking
  • Obesity, sedentary lifestyle
• Stable Angina


  • Plaque occluding ~75% or more of coronary artery
  • Causes "typical" chest pain that occurs with exertion and is relieved by rest or nitroglycerine
  • EKG at rest is normal, symptoms absent at rest
• Stress Testing


  1. Goal is to provoke and detect ischemia

  2. Provocation: exercise preferred, pharmacologic if contraindicated

  3. Detection: EKG changes, nuclear imaging, echocardiography
• Pharmacologic Stress Testing


  • Uses drugs like regadenoson, dipyrimadole, adenosine, or dobutamine to induce coronary steal and detect ischemia
  • Contraindicated in reactive airway disease/wheezing
• Stress testing identifies ischemia due to "flow-limiting" stenosis (usually >75%), but may miss non-flow-limiting lesions
• Stable Angina Management


  • Preventative therapy (aspirin, statin)
  • Anti-angina therapy (beta-blockers, calcium-channel blockers, nitroglycerine)
  • Coronary stent implantation
  • Coronary artery bypass grafting (CABG) surgery
• Coronary Stents


  • Percutaneous Coronary Intervention (PCI) to implant stents
  • Drug-eluting stents coated with polymer and drug to prevent restenosis
• Coronary Artery Bypass Grafting (CABG)


  Uses grafts like left internal mammary artery (LIMA), saphenous vein, or radial artery to bypass blocked coronary arteries
• Stable Angina Typical Case
• Stent Complications


  • Restenosis: slow, steady growth of scar tissue over stent
  • Thrombosis: acute closure of stent, life-threatening
• Stent Thrombosis Prevention


  Dual antiplatelet therapy (aspirin + P2Y12 inhibitor) for at least 1 year after stent placement
• Variant (Prinzmetal) Angina


  • Episodic vasoconstriction of coronary vessels, often at rest
  • Associated with smoking
  • Treated with calcium channel blockers, nitrates, avoid propranolol
• Acute Coronary Syndromes


  • Subtotal occlusion: Unstable angina, NSTEMI
  • Total occlusion: STEMI
• Unstable Angina and NSTEMI


  • Ischemic symptoms occurring with increasing frequency or at rest
  • ECG changes (ST depressions, T-wave inversions)
  • Positive cardiac biomarkers (troponin, CK-MB)
• Treatment of UA/NSTEMI


  1. Aspirin, beta-blocker, heparin

  2. Angioplasty (non-emergent)
• Obtain EKG in all chest pain patients, give aspirin to those with possible NSTEMI
• STEMI


  Angina at rest with ST-segment elevation, biomarkers elevated after 4-6 hours
• STEMI ECG Findings


  • Anterior ST elevations
  • Lateral ST elevations
  • Inferior ST elevations
  • Posterior ST elevations
• Special STEMI Complications


  • Right ventricular infarction in inferior STEMI
  • Sinus bradycardia and heart block in inferior STEMI
  • Cardiogenic shock in large anterior STEMI
• Treatment of STEMI


  1. Main objective is to open the occluded artery as quickly as possible (revascularization)

  2. Options: emergency angioplasty (< 90 min) or thrombolysis (< 30 min)

  3. Supportive medical therapy (aspirin, heparin, beta-blockers, nitrates)
• Cautions with beta-blockers and nitrates in STEMI
• Other STEMI treatments include clopidogrel, eptifibatide, and bivalirudin