cardio

• Abnormal Automaticity: Enhanced (acceleration of phase 4 repolarization)

  Prototype: Idiopathic VT; AT
• Abnormal Automaticity: Suppressed (absent or decelerated phase 4 repolarization): SA Node Dysfunction
• Trigerred Activity: EADs (Early afterdepolarizations): TdP in long QT syndrome; PVCs
• Triggered Activity: Delayed Afterdepolarization: Reperfusion PVCs/VT, AT and VT with digitalis toxicity
• Reentry:

  1.Anatomical or functional confinement of a circuit (i.e., scar, accessory pathway);

  2. Unidirectional block after a premature impulse

  3. Wave of excitation that travels in a single direction returning to its point of origin

  Prototype: AVNRT, AVRT, atrial flutter, scar-related VT
• Intracardiac Catheterization: Catheters are inserted along the femoral vein.
• Phases of Action Potential

  → Phase 0 - Na influx occurs

  → Phase 1 - Early repolarization

  → Phase 2 - Plateau

  → Phase 3 - Late depolarization

  → Phase 4 - Resting membrane potential
• Sleep apnea → Provokes the Bezold-Jarisch reflex, a cardio-depressor mechanism

  ▪ When you have apnea and hypoxia, Bezold-Jarisch reflex is activated, leading to hypotension
• COVID-19

  → Severe bradycardia syndrome, and postural orthostatic tachycardia syndrome are identified in patients with long Covid
• SA NODAL DYSFUNCTION

  “Sinus Arrest”; Sinus Exit Block

  → Type I

  ▪ Fixed; a certain part of the sinus node does not provoke or does not inscribe in ventricular contraction 📣

  → Type II

  ▪ Mobitz I − Takes long before you have a loss of the ventricular contraction 📣

  ▪ Mobitz II − Can be intermittent
• ● Chronotropic Incompetence → 208 - (0.7 x Age) ▪

  If you don’t achieve this heart rate by doing exercise, you may have chronotropic incompetence 📣
• AV NODE DYSFUNCTION

  FIRST-DEGREE AV BLOCK

  All atrial impulses are conducted to the ventricle

  ● Prolonged PR interval (>200 ms) without the QRS dropping

  📣 ● AV delay usually occurs within the AV node (intranodal)
• SECOND-DEGREE AV BLOCK

  ● Intermittent failure of conduction between atrium and ventricle

  2 types

  ● Type I / Mobitz I / Wenckebach -Progressive PR interval prolongation until loss of conduction occurs

  ● Type II / Mobitz II Progressive

  • Fixed PR interval before loss of conduction
  • Some of these patients are candidates for permanent pacing because the block of the AV node is below the bundle of His (infranodal) 📣
  • Usually associated with QRS widening
• THIRD-DEGREE AV BLOCK

  Complete heart block

  Complete interruption of conduction between atria and ventricles

  Complete dissociation of the natural atrioventricular (AV) pacing

  → P wave is pacing on its own, and the ventricles are conducting on its own
• In all types of AV block, permanent pacing class I is done
• A single-chamber transvenous pacemaker with the pacing lead in the right ventricular outflow tract (arrow)

  → The lead makes its way into the subclavian vein → going to the innominate → going to the right atrium
• A single-chamber leadless pacemaker (arrow) → Placed via transseptal puncture if pacing is on the left 📣 → Can also be placed on the right side → Marketed locally as Micra
• SUPRAVENTRICULAR TACHYARRHYTHMIAS

  • Heart Rate Over 120 — 200 BPM Average
  • If you repeatedly get this result or you’re not feeling well, you should talk to your doctor
  • Reported Symptoms
  • Rapid pounding, or fluttering heartbeat; Chest tightness or pain ;Fainting
  • Example: → Retrograde P waves: after the QRS, there are very small waves that look like P waves
  • Typically 150 to 180 bpm
• PHYSIOLOGIC SINUS TACHYCARDIA

  • Defining feature: normal sinus mechanism precipitated by exertion, stress, exogenous or endogenous stimulants, concurrent illness
• Inappropriate sinus tachycardia

  • Tachycardia from the normal sinus node area that occurs without an identifiable precipitating factor as a result of dysfunctional autonomic regulation
• Focal atrial tachycardia (AT)

  ● Regular atrial tachycardia with defined P wave

  ● May be sustained, nonsustained, paroxysmal, or incessant

  ● Frequent sites of origin occur along the valve annuli of left or right atrium, pulmonary veins, coronary sinus musculature, superior vena cava
• Atrial flutter and macroreentrant atrial tachycardia

  • Macroreentry reflected as organized atrial activity on an electrocardiogram (ECG), commonly seen as sawtooth flutter waves at rates typically faster than 200 beats/min
• Atrial fibrillation

  • Chaotic rapid atrial electrical activity with variable ventricular rate
  • The most common sustained cardiac arrhythmia in older adults
• Multifocal atrial tachycardia

  • Multiple discrete P waves often seen in patients with pulmonary disease during acute exacerbations of pulmonary insufficiency
• AV NODAL REENTRY TACHYCARDIA (AVNRT)

  • Paroxysmal regular tachycardia with P waves visible at the end of the QRS complex or not visible at all
  • The most common paroxysmal sustained tachycardia in healthy young adults
  • → More common in women
• Orthodromic AV reciprocating tachycardia (AVRT)

  • Paroxysmal sustained tachycardia similar to AV nodal reentry
  • During sinus rhythm, evidence of ventricular preexcitation may be present (Wolff-Parkinson-White syndrome) or absent (concealed accessory pathway)
• Preexcited tachycardia

  • Wide QRS tachycardia with QRS morphology similar to ventricular tachycardia
  • a. Antidromic AV reciprocating tachycardia - regular paroxysmal tachycardia
  • b. Atrial fibrillation with preexcitation - irregular wide-complex or intermittently wide-complex tachycardia, some with dangerously rapid rates faster than 250/min
  • c. Atrial tachycardia or flutter with preexcitation
• Regular atrial rate for patients with narrow complex tachycardia

  • 1:1 AV response
  • From the AV node, it is not filtered
  • Examples: − AVNRT − ORT − AT − Rarely atrial flutter
• AV block: more As than Vs

  • There is dissociation
  • Examples: − Atrial flutter − Atrial tachycardia − Rarely AVNRT with 2:1 block below the bundle of His
  • Cannot be diagnosed unless an intracardiac electrophysiologic study is performed
• VA block: more Vs than As

  • Narrow complex, more ventricular contraction
  • No P wave preceding the tachycardia
  • Example: − Junctional tachycardia
• Irregular atrial and ventricular rates

  Atrial fibrillation

  ▪ No discernable P wave

  Multifocal atrial tachycardia

  ▪ Characterized by a rhythm with ≥ 3 distinct P-wave morphologies with rates typically between 100 and 150 bpm and an isoelectric baseline between P waves
• Diagnostic effect of increasing AV Node Blockade using adenosine or vagal reflex maneuver

  
• Vagal maneuvers include:
• Holding breath while bearing down to increase intrathoracic pressure
• Straining by increasing strain in abdominal cavity by increasing vagal tone
• Breathing hard into a syringe against pressure to increase intrathoracic pressure
• Raising legs abruptly to increase venous return
• Diver’s reflex: Submerge face into cold water
• Carotid sinus massage:

  • Hold the area of the jaw where it bifurcates into the internal and external carotid and where the carotid sinus is
  • Stimulating it should result in a vagal effect, slowing down the heart rate
  • If no improvement within 10 seconds, proceed to pharmacologic intervention
• Adenosine:

  • Done if carotid sinus massage doesn’t work and if there are no contraindications