Cardiovascular Pathophysiology PDF Lecture Notes

Cardiovascular Pathophysiology (3/4) Ricardo L. Garcia MD TODAY’S LECTURE } Abnormalities of Cardiac Conduction } Cardiac Rhythm Let’s get in tune You walk into the perioperative area to meet your patient, pull back the curtain, and find the patient with the following rhythm. After assessing...

Cardiovascular Pathophysiology (3/4) Ricardo L. Garcia MD TODAY’S LECTURE } Abnormalities of Cardiac Conduction } Cardiac Rhythm Let’s get in tune You walk into the perioperative area to meet your patient, pull back the curtain, and find the patient with the following rhythm. After assessing the patient and finding no pulse and no respirations, what is the first thing you would do? a) b) c) d) e) } Give pericardial thump Defibrillate at 200 joules Give lidocaine 1 mg/kg intravenously Give epinephrine 1mg/kg intravenously Synchronized cardioversion at 360 joules Let’s get in tune } You walk into the perioperative area to meet your patient, pull back the curtain, and find the patient Which of the following is the best description of second degree heart block type II (Mobitz II)? a) b) c) d) e) A prolonged PR interval greater than 0.2 seconds A constant and set PR interval; the ventricular rate is slower than the atrial rate Progressive lengthen of the PR interval No electrical relationship between the atria and the ventricles An atrial rhythm less than 60 Anatomy Review Pacemakers and conduction System Cardiac Conduction System ECG Correlation Electrophysiology } Impulses: progressive depolarization } Membrane potential : } } } Sodium imbalance 3 Potassium arrhytm ATPase * causes / as Pacemaker Action Potential Action Potentials Sa node punjinkefiber ECG Determine Heart Rate ECG - 200ms Cardiac Dysrhytmias Mechanisms Supraventricular } Abnormalities in: } Heart Rate Site of Abnormality } Classification: } } } } } Tachydysrhytmias Bradydysrhytmias Atrial Vs Ventricular All of the above Problem : above ventricles Tachydysrhytmias } Pathophysiology } Increased Automaticity } Triggering of abnormal cardiac potentials (after depolarization) } Reentry of electric potentials (most common) Tachydysrhytmias } Pathophysiology: Reentry of electric potentials Supraventricular Dysrhythmias } Sinus Dysrhythmia } } } Normal variation with respiration: INSPIRE=INCREASE HR Bainbridge Reflex Sinus Tachycardia } } Usual : 100 – 160 beats per minute Normal ECG } } } pain , fever , anMous P before each QRS PR interval ‘normal’ Normal physiological response, well tolerated except in presence ofO-M IHD risk for infarct Supraventricular Dysrhythmias } Perioperative management: } Sinus Dysrhythmias and Sinus Tachycardia } Look for underlying cause, and treat as necessary } Consider β-blocker if hemodynamically stable in the presence of& IHD -> consider cardio eval } Avoid vaogolytic drugs (pancuronium) - Supraventricular Dysrhythmias } Premature Atrial Contractions (PAC) } Ectopic beat from the atria } Abnormal p wave } Variable PR interval } Normal QRS Supraventricular Dysrhythmias } Premature Atrial Contractions (PAC) } Symptoms: Heavy heart beat; most asymptomatic } Most common seen at rest; and seen at all ages. } } Not a risk factor for a life threatening dysrhytmia Second most common arrhythmia associated to acute MI 1 . Sinustach -> atblduring management) Supraventricular Dysrhythmias } Premature Atrial Contractions (PAC) } Perioperative management: } } } } Avoid precipitating drugs: caffeine, nicotine Evaluate digitalis levels Avoid excessive sympathetic stimulation ↳ Will stimulate arrhythmias Only treat if secondary dysrhythmias develop: β-blocker ¨ Calcium channel blocker ¨ Supraventricular Dysrhythmias ↳ treatment ? } vagal adenosine Supraventricular Tachycardia (SVT) } Tachydysrhythmia: 160 to 180 beats per minute } initiated and sustained by tissue at or above the AV node. is sudden development } usually paroxysmal and may begin and end very abruptly. } AV nodal reentrant tachycardia (AVNRT) is the most common type } Other mechanisms: } enhanced automaticity of secondary pacemaker cells and triggered impulse initiation by afterdepolarizations. Supraventricular Dysrhythmias } Supraventricular Tachycardia (SVT) } Symptoms: } } } } } } } } Light headness Dizziness Fatigue Chest discomfort Dyspnea Syncope Polyuria : atria dilation . Natriuretic Peptide increase Most common in young woman without structural heart disease Supraventricular Dysrhythmias } Supraventricular Tachycardia (SVT) } Perioperative management: Correct it! } Hemodynamically stable ¨ Vagal manuvers ¨ Adenosine IV } Hemodynamically unstable ¨ Adenosine ¨ β-blocker ¨ Synchronized cardioversion Supraventricular Dysrhythmias } Supraventricular Tachycardia (SVT) Supraventricular Dysrhythmias } Multifocal Atrial Tachycardia (MAT) } Irregular rhythm } Several distinct p wave morphology } Variable PR interval } Most commonly seen in patients with COPD exacerbation ↳ It pulmonary diferentes P HTN Supraventricular Dysrhythmias } Multifocal Atrial Tachycardia } Perioperative management: Treat underlying cause: Exacerbation? } Magnesium sulfate } Calcium channel blockers help ↓ Pulmonary HTN } Avoid theophylline sympathomimetic will arrhythmic } Avoid Hypoxemia } Cardioversion: NO EFFECT } - cause Supraventricular Dysrhythmias } Atrial Flutter } An organized atrial rhythm: 250 to 350 bpm with varying degrees of AV block. Saw tooth appearance on ECG: flutter waves. Ventricular rate of 2:1 Commonly associated to: e n - } } } } } } } atrial fibrillation atrial tachycardia. structural heart disease Other conditions: pulmonary disease, acute myocardial infarction, ethanol intoxication, or thyrotoxicosis, or after cardiothoracic surgery. variable Supraventricular Dysrhythmias } Atrial Flutter } Perioperative management: Treatment } Control exacerbation conditions } If present >48hrs: anticoagulation } Hemodynamically Unstable: ¨ Cardioversion: low } dose 50J Hemodynamically Stable: ¨ Override pacing ¨ Control ventricular rate: AV conduction ¨ ¨ ¨ -S Amiodarone Diltiazem Verapamil using this to ↓ ventricle response Supraventricular Dysrhythmias } Atrial Fibrillation } No discernible p waves } May be cause by other atrial tachycardia } Variable Ventricular response rate } May trigger Ventricular tachycardia in predisposed patients } Predisposing Conditions: } } } } } HBP IHD COPD pulmonar HTN Pericarditis Valvular disease: large atrias ~ - Reg · or aortic stenosis Supraventricular Dysrhythmias } Atrial Fibrillation Supraventricular Dysrhythmias } Atrial Fibrillation } Perioperative management/treatment: } Most patients can be asymptomatic } Most common sustained dysrhythmia } Incidence increases with age HTN } Highly associated with HBP and IHD } High risk for thrombus formation;: Need anticoagulation Supraventricular Dysrhythmias } Atrial Fibrillation } Perioperative management/treatment: } Control Ventricular response ¨ Calcium channel ¨ Beta blockers ¨ Digoxin } Spontaneous resolution Vs Pharmacologic Conversion: ¨ Amiodarone - preffered ti ↓ velocity ↓ co e ¨ Propafenone ¨ Sotalol Supraventricular Dysrhythmias } Atrial Fibrillation } Perioperative management/treatment: } Post pone surgery until controlled } If intraoperative: Sync-Cardioversion 100-200J biphasic } Atrial fibrillation is the most common post operative tachycardia in the first 2-4 days } Monitor magnesium and digoxin levels Ventricular Dysrhythmias } Premature Ventricular Contraction (PVC) } Source below AV node; Uni- or Multi focal } Premature and wide QRS } No P wave } ST segment and T wave opposite to normal } Compensatory pause compensatory pause Ventricular Dysrhythmias } Premature Ventricular Contraction (PVC) } } } may be self limited and asymptomatic More than 3 consecutive: Ventricular tachycardia R on T phenomenon predispose to rtach Ventricular Dysrhythmias } PVC: Perioperative management } } } } No mayor risk in healthy individuals without structural heart disease Frequent PVCs (>6 /min) and repetitive or multifocal procedure & Cardiology forms of ventricular ectopy indicate an increased risk of developing a life-threatening tachydysrhythmia. Usually seen in arterial hypoxemia, IHD, valvular heart disease, cardiomyopathy, QT interval prolongation, digitalis toxicity, and electrolyte abnormalities. Excessive caffeine, alcohol, and cocaine use can also cause PVCs. electrolyte abnormalities ↳ stop MK follow or k w . Ventricular Dysrhythmias } PVC: Perioperative management } Determine if underlying cause } } Including intra atrial catheters Frequent PVC’s should be treated: } β-blockers } Amiodarone and others: only if develop tachyarrhythmia's } Resolve acidosis, electrolyte imbalance : magnesium & Ventricular Dysrhythmias } Ventricular tachycardia ( VT) } Ventricular dysrhythmias occur in 70% to 80% of persons older than age 60 } Risk of sudden death in structurally normal hearts is low. } Treatment with a β-blocker or calcium channel blocker can suppress the dysrhythmia and alleviate symptoms. } Catheter ablation or implantation of a cardioverter or defibrillator are options for treatment of drug-refractory ventricular tachycardia. Ventricular Dysrhythmias } Ventricular tachycardia ( VT) magnesio to ↓ most common cause related w not is no pulle * . hypomagn . Ventricular Dysrhythmias } VT: perioperative / Management } Symptomatic or unstable monomorphic ventricular tachycardia or SVT should undergo cardioversion immediately. } } 100 J (monophasic) and increase in increments of 50 to 100 J as necessary. Recurrent VT ¨ Amiodarone 150 mg over 10 minutes is recommended. ¨ Alternative drugs include procainamide, sotalol, and lidocaine. } Pulseless ventricular tachycardia or polymorphic ventricular tachycardia under any circumstances requires initiation of cardiopulmonary resuscitation (CPR) and immediate defibrillation using 360 J (monophasic). Ventricular Dysrhythmias } Ventricular fibrillation ( Vfib) } Most common cause of sudden death } Usually associated to IHD ischemic Heart disease } Long term treatment: implantation implantable pacemaker } A pulse never present in Vfib, if patient awake and I taking: re evaluate! Vfib: management } ACLS !!!!!!!!!! } ? 2 . Shock 2 . CPR 3 . 1 Ruthen! Check shockShout ? yes inlubale - H ~ 5 Sp epi ↳ Rhythm . show. stack - 200 Amio .. oo Biphasic & · s Monod I i Amidmaint br 30 s oug de si IF Eren Ventricular Dysrhytmias } Wolff-Parkinson-White Syndrome (WpW) } } The diagnosis of WPW syndrome is reserved for conditions characterized by both preexcitation and tachydysrhythmia. Ventricular preexcitation causes an earlier than normal deflection of the QRS complex called a delta wave. Delta waves can mimic the Q waves of a myocardial infarction. Ventricular Dysrhytmias } Wolff-Parkinson-White Syndrome (WpW) antidrom. se va donde por ) no ↑se supithe Drugs that slow AV nodal conduction, such as adenosine, calcium channel blockers, β-blockers, lidocaine, and digoxin, may increase conduction along the accessory pathway and are contraindicated. Facilitation of conduction over the accessory pathway may produce a marked increase in ventricular rate. Ventricular Dysrhytmias } Wolff-Parkinson-White Syndrome (WpW) } More common in patients with Ebstein's malformation of the tricuspid valve, hypertrophic cardiomyopathy, and transposition of the great vessels. } Bimodal age distribution: early childhood vs young adulthood. } Paroxysmal palpitations with or without dizziness, syncope, dyspnea, or angina pectoris are common symptoms. } Incidence of sudden cardiac death low