SVA Pathophysiology Lecture Study Guide 2024 PDF

**[Pathophysiology of Supraventricular arrhythmias ]{.smallcaps}** **IP: Cardiology** **Fall 2024** **Anastasia L. Armbruster, Pharm.D., FACC, BCCP** Professor of Pharmacy Practice St. Louis College of Pharmacy at UHSP Email: **Mechanisms of cardiac arrhythmias** - Automatic tachycardia *...

**[Pathophysiology of Supraventricular arrhythmias ]{.smallcaps}** **IP: Cardiology** **Fall 2024** **Anastasia L. Armbruster, Pharm.D., FACC, BCCP** Professor of Pharmacy Practice St. Louis College of Pharmacy at UHSP Email: **Mechanisms of cardiac arrhythmias** - Automatic tachycardia **=** abnormality in impulse generation - Impulses initiated by cardiac tissues other than SA node - Onset not related to initiating event (i.e. premature impulse) - Reentrant tachycardia = abnormality in impulse conduction - Necessities for reentry mechanism: - Two pathways of conduction - A unidirectional block in one pathway - Slow conduction in other pathway **Normal Sinus Rhythm** **Normal Sinus Rhythm** ------------------------- ------------------------------------------------------------ Ventricular rate 60-100 bpm Rhythm Regular P waves Present and similar in appearance, followed by QRS complex P:QRS ratio 1:1 **Sinus Tachycardia** - Increased automaticity in SA node - Etiologies - Exercise, infection, anxiety, pain, caffeine, hyperthyroidism, hypotension, dehydration **Sinus Tachycardia** ----------------------- ------------  Ventricular rate \> 100 bpm Rhythm Regular P waves Present P:QRS ratio 1:1 **Sinus Bradycardia** - Decreased automaticity in SA node - Etiologies - Drugs that exhibit negative chronotropic effects (decreased HR) - Increased parasympathetic nervous system - Hypothyroidism, hypothermia, hypoxia **Sinus Bradycardia** ----------------------- ------------------------------------------------------------------------ Ventricular rate \< 60 bpm Rhythm Regular P waves Present and similar in appearance, immediately followed by QRS complex P:QRS ratio 1:1 **Arrhythmias** +-----------------+-----------------+-----------------+-----------------+ | **HR \> 100 | **HR 60-100 | **HR \< 60 | **No rate** | | bpm** | bpm** | bpm** | | | | | | | | **(Tachyarrhyth | | **(Bradyarrhyth | | | mias)** | | mias)** | | +=================+=================+=================+=================+ | Supraventricula | Normal sinus | AV block | Asystole | | r | rhythm | | | | arrhythmias: | | - 1^st^ | | | | | degree | | | - Atrial | | | | | flutter | | - 2^nd^ | | | (Aflutter) | | degree | | | | | | | | - Atrial | | - 3^rd^ | | | fibrillatio | | degree | | | n | | | | | (AF) | | | | | | | | | | - Paroxysmal | | | | | supraventri | | | | | cular | | | | | | | | | | - tachycardia | | | | | (PSVT) | | | | | | | | | | Ventricular | | | | | arrhythmias: | | | | | | | | | | - Premature | | | | | Ventricular | | | | | Contraction | | | | | s | | | | | (PVCs) | | | | | | | | | | - Ventricular | | | | | tachycardia | | | | | (VT) | | | | | | | | | | - Torsades de | | | | | Pointes | | | | | (TdP) | | | | | | | | | | - Ventricular | | | | | fibrillatio | | | | | n | | | | | (VF) | | | | +-----------------+-----------------+-----------------+-----------------+ **Supraventricular arrhythmias** +-----------------------+-----------------------+-----------------------+ | **Arrhythmia** | **Pathophysiology** | **Etiology** | +=======================+=======================+=======================+ | Atrial Flutter | Reentry within right | Cardiac vs. | | | atria | non-cardiac (see | | | | below) | +-----------------------+-----------------------+-----------------------+ | Atrial Fibrillation | Reentry from multiple | Cardiac vs. | | | atrial foci | non-cardiac (see | | | | below) | +-----------------------+-----------------------+-----------------------+ | Paroxysmal | Reentry at AV node | Excessive caffeine | | Supraventricular | | | | Tachycardia (PSVT) | | Alcohol use | | | | | | | | Illicit drug use | +-----------------------+-----------------------+-----------------------+ | Wolff-Parkinson-White | Reentry outside AV | Typically present at | | (WPW) | node (Bundle of Kent) | birth | +-----------------------+-----------------------+-----------------------+ **Pathophysiology Mechanism** - All of the above listed supraventricular arrhythmias work by the reentry mechanism - Reentry - Continuous propagation of impulse due to continued activation of refractory tissue - For reentry to occur you need the following: - 2 pathways of conduction, one fast & one slow - An area of unidirectional block (think: a one way street) - The fast pathway conducts the impulse very fast, but is slow to reset itself to conduct a second impulse - Fast conduction, long refractory period - The slow pathway conducts the impulse very slowly, but can reset itself to conduct a second impulse very quickly - Slow conduction, short refractory period - So what makes each arrhythmia different? - Location! - Aflutter: reentry occurs in the right atria [only], and only one spot (area of focus) at a time - Afib: reentry occurs anywhere within the right or left atria, and occurs at multiple spots at once (multiple atrial foci) - PSVT: reentry occurs [at] the AV node - WPW: reentry occurs [outside] the AV node (think: secret passageway, aka Bundle of Kent, to the ventricles) **PSVT (AV nodal reentry)** ----------------------------- ---------------------------------------------  Ventricular rate 150-250 bpm Rhythm Regular P waves Often unseen or superimposed on QRS complex **Wolff-Parkinson-White (AV reentry with accessory pathway)** --------------------------------------------------------------- ----------------------------------------------------- Ventricular rate \> 100 bpm Rhythm Regular P waves Present QRS complex Usually prolonged (\> 0.12 sec), delta wave present **Atrial Flutter** ----------------------- -----------------------------------------------------  Atrial rate 250-350 bpm Ventricular rate 120-180 bpm Rhythm Irregular P waves Absent, replaced by "sawtooth" or "flutter" pattern P:QRS ratio Not equal (more "flutter" waves than QRS complexes) **Atrial Fibrillation** ------------------------- ---------------------------------------------------------- Atrial rate \> 350 bpm Ventricular rate 120-180 bpm Rhythm Irregularly irregular P waves Absent, replaced by "fibrillatory" waves P:QRS ratio Not equal (more "fibrillatory" waves than QRS complexes) **[\ ]{.smallcaps}** **[Atrial fibrillation ]{.smallcaps}** **Epidemiology** - Most common arrhythmia - One in four middle-aged adults in Europe and the US will develop AF - Approximately 2% of people younger than age 65 have AF, while about 9% of people aged 65 years or older have AF - Increased prevalence due to: - Better detection of silent AF - Increasing age - Conditions predisposing to AF **Morbidity & Mortality** - Major cause of stroke, heart failure, sudden death, and cardiovascular mortality - AF independently associated with increase in all-cause mortality (2-fold in women, 1-5-fold in men) **Pathophysiology** - Caused by rapid & disorganized conduction in left and right atria leading to loss of mechanical contraction - Multiple reentrant loops - Results in irregular activation of the ventricles and [irregularly irregular pulse] - No single impulse depolarizes atria completely, leading to disorganized atrial activity and contraction - Disorganized atrial contraction results in loss of atrial kick **Diagnosis** - Electrocardiogram - Implantable devices - Physical exam - Not confirmatory, but can detect irregularities in pulse - Electronic devices - AliveCor - Apple Watch 4 **Collect** - Chief complaint - Some patients will have no symptoms (25-40%) - Worst case: Embolic event (stroke) or HFrEF present upon diagnosis - Potential symptoms: Palpitations, chest pain, dyspnea, fatigue, light-headedness, syncope/near syncope - Factors affecting symptoms: ventricular rate, LV function, duration, patient perceptions - Past medical history - Social history - Tobacco/alcohol use, exercise habits, diet - Patient characteristics (age, sex) - History of present illness (signs/symptoms of AF, duration of AF symptoms) - Current medications - Review of systems and physical exam - Vitals: blood pressure and heart rate - Signs and symptoms - Laboratory values and diagnostics - Electrolytes (potassium and magnesium) - Serum creatinine - Thyroid function tests - 12-lead electrocardiogram (ECG) - Echocardiogram **Differential diagnosis** Can be difficult due to wide variety of symptoms! - Other arrhythmias - Heart failure - Pulmonary embolism - Acute coronary syndromes **Assess** +-----------------------------------+-----------------------------------+ | Assessment | Definition/Method of | | | Justification | +===================================+===================================+ | Statement of the Problem | | +-----------------------------------+-----------------------------------+ | Duration | | +-----------------------------------+-----------------------------------+ | | Current episode is first | | | documented episode | +-----------------------------------+-----------------------------------+ | Frequency | | +-----------------------------------+-----------------------------------+ | | AF that terminates spontaneously | | | or with intervention within 7 | | | days | | | | | | Episodes may recur with variable | | | frequency | +-----------------------------------+-----------------------------------+ | | Continuous AF that is sustained | | | \> 7 days | +-----------------------------------+-----------------------------------+ | Longstanding Persistent | Continuous AF of longer than 12 | | | months | +-----------------------------------+-----------------------------------+ | | AF that is accepted by the | | | patient (and physician). NSR is | | | no longer attempted | +-----------------------------------+-----------------------------------+ | Pattern | | +-----------------------------------+-----------------------------------+ | | EKG shows irregularly irregular | | | rhythm with absence of p waves | | | and presence of fibrillatory | | | waves | +-----------------------------------+-----------------------------------+ | Etiology | | +-----------------------------------+-----------------------------------+ | | CAD, valvular disease, heart | | | failure | +-----------------------------------+-----------------------------------+ | | HTN, obesity, diabetes, chronic | | | kidney, disease, sleep apnea, | | | hyperthyroidism, acute infection, | | | excessive alcohol/drugs, | | | excessive caffeine, post-surgery, | | | pulmonary embolism, increasing | | | age (\>60 years), lack of | +-----------------------------------+-----------------------------------+ | Status/Severity | | +-----------------------------------+-----------------------------------+ | Presence of symptoms | Presence of symptoms (list | | | patient specific symptoms) | | | | | | No symptoms present | +-----------------------------------+-----------------------------------+ | Rate control | Goal \< 110 bpm or \< 80 bpm in | | | patients who are symptomatic or | | Heart rate controlled to goal | w/ HFrEF | | | | | Controlled ventricular rate | HR \< 110 bpm | | | | | | HR ≥ 110 bpm | +-----------------------------------+-----------------------------------+ | Risk Factors | | +-----------------------------------+-----------------------------------+ | Stroke risk factors | **C**ongestive Heart Failure | | | (HFpEF and HFrEF) | | (CHA~2~DS~2~-VASc Score 0-9) | | | | **H**TN | | | | | | **A**ge \> 75 years (2 points) | | | | | | **D**iabetes | | | | | | **S**troke or TIA (2 points) | | | | | | **V**ascular disease (prior MI, | | | PAD, aortic plaque) | | | | | | **A**ge 65-74 | | | | | | **S**ex **c**ategory (female) | +-----------------------------------+-----------------------------------+ | Complications | | +-----------------------------------+-----------------------------------+ | Mortality | EF ≤ 40% | | | | | Stroke | Volume overload with elevated BNP | | | | | HFrEF | SBP \< 90 mmHg & HR ≥ 110 bpm | | | | | Heart failure exacerbation | Requires inpatient hospital stay | | | for management | | Hemodynamic instability | | | | | | Hospitalization | | +-----------------------------------+-----------------------------------+ **AF Etiologies & Contributing Physiology** **Atrial Distension** **High Adrenergic Tone** ----------------------------- ------------------------------------------------------ **Chronic hypertension** Sepsis Mitral valve disease Hyperthyroidism **Cardiomyopathy** **Binge drinking** Congenital defects **Alcohol withdrawal** **Acute pulmonary embolus** **Excessive caffeine** Pulmonary hypertension **Sympathomimetics such as cocaine or amphetamines** **Myocardial ischemia** Surgery **\*Responsible for bolded terms** **Heart Failure & AF** - Coincide in many patients - Up to 50% of patients with Stage IV HFrEF - Increases mortality risk - Linked by similar risk factors and share a common pathophysiology - Can exacerbate each other through structural remodeling, activation of neurohormonal mechanisms and rate-related impairment of LV function - For patients who develop HF as a result of AF, rhythm-control is indicated - One of the few reversible causes of HF **Stroke Risk: CHADS~2~-VASc Score** Score Annual Stroke Risk (%) ------- ------------------------ 0 0 1 1.3 2 2.2 3 3.2 4 4 5 6.7 6 9.8 7 9.6 8 6.7 9 15.2 **Bleeding Risk: HAS-BLED Score** - Score of ≥ 3 indicates "high" risk for bleeding - Does not usually result in withholding anticoagulation - Increased monitoring - Eliminating risk factors when possible - Hypertension (\> 160 mmHg) - Abnormal renal function - Abnormal liver function - Stroke - Bleeding history - Labile INR - Elderly (\> 65 years of age) - Use of drugs that promote bleeding (NSAIDS, anti-platelets) - Alcohol use **Case 1** An 82-year-old man presents to the ED with complaints of chest pain, SOB, and a "funny, fast heart beat." He reports having felt this way since last night and has "never" felt like this before. His PMH includes history of a MI in 2000, hypertension, and diabetes. After examination, his vitals and lab work are as follows: BP 88/52 mmHg HR 146 bpm RR 18 bpm Na 137 mEq/L K 4.2mEq/L Scr 1.0 mg/d An EKG reveals an irregularly irregular rhythm with absent p waves +-----------------------------------+-----------------------------------+ | Assessment | Justification | +===================================+===================================+ | Statement of the problem | | +-----------------------------------+-----------------------------------+ | Etiology | | +-----------------------------------+-----------------------------------+ | Status | | +-----------------------------------+-----------------------------------+ | Stroke Risk Factors | | | | | | CHA~2~DS~2~-VASc | | +-----------------------------------+-----------------------------------+ | Complications | | +-----------------------------------+-----------------------------------+ **Case 1a** Write a scenario to correspond with each frequency classification **Frequency** **Patient scenario** ------------------------- ---------------------- Paroxysmal Persistent Longstanding persistent Permanent **Case 2** A 48-year-old man presents to his PCP with palpitations. This has happened once before after binge drinking and cocaine use. At the time, he underwent an electrical cardioversion and was discharged from the hospital the next day. BP 146/76 HR 98 bpm RR 17 bpm EKG: irregularly irregular, absent p waves +-----------------------------------+-----------------------------------+ | Assessment | Justification | +===================================+===================================+ | Statement of the problem | | +-----------------------------------+-----------------------------------+ | Etiology | | +-----------------------------------+-----------------------------------+ | Status | | +-----------------------------------+-----------------------------------+ | Stroke Risk Factors | | | | | | CHA~2~DS~2~-VASc | | +-----------------------------------+-----------------------------------+ | Complications | | +-----------------------------------+-----------------------------------+ **Case 3** RA is a 77-year-old man (6'2", 190 lbs) who complains of a racing heartbeat, dizziness and SOB for the past day. BP: 152/88 mmHg, P: 132 bpm, RR: 20 bpm PMH: HTN HFrEF (EF 34%) Home medications: Diabetes EKG: Irregularly irregular rhythm with fibrillatory waves +-----------------------------------+-----------------------------------+ | Assessment | Justification | +===================================+===================================+ | Statement of the problem | | +-----------------------------------+-----------------------------------+ | Etiology | | +-----------------------------------+-----------------------------------+ | Status | | +-----------------------------------+-----------------------------------+ | Stroke Risk Factors | | | | | | CHA~2~DS~2~-VASc | | +-----------------------------------+-----------------------------------+ | Complications | | +-----------------------------------+-----------------------------------+ **Case 4** A 67-year-old woman with a history of HTN and AF for 6 months visits her primary care physician today after a recent emergency department visit for increased fatigue on exertion, palpitations, and lower extremity edema. Her vital signs today include BP 115/70 mmHg, and HR 88 beats/min, all laboratory values are within normal limits; however, her lower extremity edema has worsened. EKG shows atrial fibrillation. An echocardiogram today shows a LVEF 35%-40%. Home medications: Ramipril 5 mg twice daily Furosemide 40 mg daily Digoxin 0.125 mg daily Warfarin 5 mg daily +-----------------------------------+-----------------------------------+ | Assessment | Justification | +===================================+===================================+ | Statement of the problem | | +-----------------------------------+-----------------------------------+ | Etiology | | +-----------------------------------+-----------------------------------+ | Status | | +-----------------------------------+-----------------------------------+ | Stroke Risk Factors | | | | | | CHA~2~DS~2~-VASc | | +-----------------------------------+-----------------------------------+ | Complications | | +-----------------------------------+-----------------------------------+ **Case 5** A 78-year-old woman presents for follow-up to her cardiologist's office. She has had AF for the past 4 years and is no longer pursing NSR. Her pacemaker was interrogated and reported an 89% atrial fibrillation burden. PMH includes HTN and stroke. She reports no symptoms today. Vitals today: 132/78 mm HG, HR 72 bpm. +-----------------------------------+-----------------------------------+ | Assessment | Justification | +===================================+===================================+ | Statement of the problem | | +-----------------------------------+-----------------------------------+ | Etiology | | +-----------------------------------+-----------------------------------+ | Status | | +-----------------------------------+-----------------------------------+ | Stroke Risk Factors | | | | | | CHA~2~DS~2~-VASc | | +-----------------------------------+-----------------------------------+ | Complications | | +-----------------------------------+-----------------------------------+