The Massachusetts General Hospital Handbook of Neurology

Authors: Flaherty, Alice W.; Rost, Natalia S.

Title: Massachusetts General Hospital Handbook of Neurology, The, 2nd Edition

Copyright 2007 Lippincott Williams & Wilkins

> Table of Contents > Medicine > Heart

Heart

A. Cardiac code calls

• What you need: Call code team; bag-valve ventilator, 12-lead EKG; cardiac and oxygen monitor; large-bore IV access; stat blood gas, electrolytes, and CBC; defibrillator and code cart. Arrange for an ICU bed.

• Basic life support: For all cases, two initial breaths, then compressions 80-100 per minute.

  • One rescuer: 15:2 ratio of compressions to ventilations.

  • Two rescuers or pediatric: 5:1 ratio of compressions to ventilations.

• Advanced cardiac life support: See Figures 31 and 32.

B. Neurological complicaions of heart dz

Embolic stroke, global hypoxia. MIs are RFs for stroke and vice versa. A fib, mechanical valves, and LV thrombus are all reasons for anticoagulation to prevent stroke.

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P.205

C. Arrhythmia

• See also: Electrocardiogram, p. 207.

• H&P: Is pt. symptomatic during arrhythmia? What drugs is pt. on? Freq, duration, what triggers and stops rhythm.

• Tests: EKG (compare with old), electrolytes, Ca, Mg, TSH, ABG, drug levels, CXR.

• Atrial fibrillation (A fib):

  • Causes: Ischemia, PE, thyroid, drugs, conduction system problem, alcohol binge, post heart surgery.

  • EKG: Absent P waves. If QRS is wide, consider V tach.

  • Rx of new A fib: Consider cardiology consult if unable to control rate. Unstable pts. may require immediate cardioversion.

    • Diltiazem: Bolus 20 mg IV over 2 min; may repeat in 15 min. Consider verapamil or -blockers (i.e., metoprolol 5 mg IV q5min 3). Always give oral dose once rate controlled, as IV dosing wears off quickly.

    • Digoxin: 0.5 mg IV, then 0.25 mg PO q8h 2, then 0.125-0.25 mg qd. Takes time for effect not always the first-line agent. See Digoxin, p. 168.

    • Contraindications to A fib drugs:

      • Wide QRS complex: May actually be V tach, in which Ca channel blockers may be lethal. Consider adenosine. Treat like V tach: 75 mg lidocaine, cardiovert.

      • Hypotension.

      • Plan for DC cardioversion: Digoxin may make cardioversion dangerous.

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    • DC cardioversion: Emergent if there is angina, low BP, CHF.

    • Anticoagulation: See Anticoagulants, p. 160.

• AV block:

  • 1st degree = Long PR. Do not treat unless bradycardic. Consider digoxin toxicity as cause.

  • 2nd degree:

    • Mobitz I (Wenckebach): Above bundle of His.

      • EKG: Gradual PR lengthening, narrow QRS, RR gradually shorter.

      • Rx: Usually benign. If pt. is symptomatic or if there is bundle branch block, give atropine or pace.

    • Mobitz II: The lesion is usually below the bundle of His. May go to complete heart block.

      • EKG: PR constant; usually wide QRS; occasional nonconducted P wave.

      • Rx: Cardiology consult. Needs pacer even if pt. is asymptomatic. In the mean time, if symptomatic, use atropine, isoproterenol, or external pacing.

  • 3rd degree: Complete heart block. Treat as Mobitz II, but more urgently.

• Bradycardia: See Cardiac code calls, p. 203.

• Junctional rhythm:

  • EKG: Narrow QRS but no P waves.

  • Rx: Treat underlying condition (ischemia, dig toxicity). Treat paroxysmal junctional tach like SVT, but carotid massage does not work as well.

• Premature beats: (PACs, PVCs). Usually treat only if pt. is symptomatic, but check with cardiology some PVCs are malignant.

• Supraventricular tachycardia (SVT, AKA PSVT):

  • DDx: V tach; rapid A fib, sinus tach.

  • EKG: Narrow-complex tachycardia always preceded by P waves. Tachycardia can cause ST depression and T wave inversion, without ischemia, even after tachycardia has resolved.

  • Rx: See Cardiac code calls, p. 203. Consult cardiology.

    • Adenosine if narrow-complex tachycardia.

      • Dosing: Run rhythm strip; give 6-12-12 mg rapid bolus through peripheral IV (3-6-6 if central line) q1-2min.

      • Complications: Watch for bronchospasm and low BP. If pt. is on theophylline, adenosine may not work.

      • Specific conditions: Okay to use in Wolff-Parkinson-White (WPW). In A fib/flutter, adenosine will uncover a string of nonconducted Ps.

    • Cardioversion if pt. has angina, hypotension, or CHF.

    • Carotid sinus massage Valsalva maneuver. Need IV access and EKG monitoring. Rule out bruits first. Massage carotids only one side at a time: 10 sec on R; if no response, then 10 sec on L. This may convert A flutter to A fib.

    • Nodal blockers:

      • Contraindications: Avoid in wide-complex tachycardia, hypotension.

      P.207

      • Verapamil: 5-10 mg IV over 2-3 min.

      • Beta-block: Propranolol 0.15 mg/kg at 1 mg/min, or esmolol if h/o asthma.

      • Digoxin: 0.5-0.75 mg IV/PO, then 0.25 mg q2h as needed.

• Torsades de pointes:

  • Causes: Things that lengthen QT interval, e.g., bradycardia, antiarrhythmics; phenothiazines; low K, Mg, or Ca; cerebral hemorrhage, ischemia, cardiomyopathy, congenital long QT, erythromycin + Seldane.

  • EKG: QRS height varies sinusoidally, HR 160-180. Long QTc.

  • Rx: Consult cardiology. Stop offending drugs. Give magnesium. Treat drug or metabolic imbalance. Consider lidocaine, phenytoin, isoproterenol (cautious if CAD), overdrive pacing.

• Ventricular fibrillation (V fib): Call a code. see p. 203.

• Ventricular tachycardia (V tach):

  • DDx: Aberrantly conducted SVT (15%, usually with RBB), tachycardic A fib. When in doubt, treat as V tach.

  • Causes: Ischemia, MI recovery (especially with post-MI aneurysm), cardiomyopathy, prolonged QT, mitral valve prolapse, drug toxicity, metabolic disturbance.

  • EKG: >6 wide QRSs at 100-200 bpm. ST and T changes in direction opposite to major QRS deflection. LAD (compared with axis in sinus). AV dissociation. Monophasic or biphasic RBBB QRSs with LAD and R/S <1 in V6.

  • Rx:

    • Sustained V tach: Call a code. see p. 203.

    • Nonsustained V tach: Consult cardiology immediately. Treat V tach if pt. is symptomatic during V tach or if runs are increasing in frequency or length (this has high risk of V fib).

• Varying rhythm:

  • Identical Ps: Suggests sinus arrhythmia; observe.

  • Changing Ps: Suggests wandering atrial pacemaker or multifocal atrial tachycardia.

    • Causes: COPD, hypoxia, digoxin toxicity, mitral regurgitation, myocard. scar.

    • Rx: Correct hypoxia, electrolytes; try verapamil or diltiazem, beta-block (not if COPD), consider Ia antiarrhythmics, amiodarone. Avoid digoxin.

  • No P waves: Suggests A fib.

D. Electrocardiogram

• Compare all EKGs to old ones.

• Heart rate: Normally 60-100. One box = 0.04 sec.

• Rhythm: Look at both Ps and QRSs. If there is arrhythmia (see Arrhythmia, p. 205), ask:

  • What is relation between P and QRS? Ps best seen in leads II and V1. Should be upright there.

  • Wide or narrow QRS?

  • QRS regular or irregular?

• Intervals:

  • PR: 3-5 boxes. <0.12 sec suggests WPW; >0.2 sec = AV block.

  P.208

  • QRS: >3 boxes (0.12) suggests ventricular arrhythmia or bundle branch block (BBB). Look in widest QRS, usually V1, V5.

  • QT: 7-10 boxes (0.28-0.40 sec) for normal rate.

    • QTc = QT/(RR interval)^1/2. Less than 0.42 for men, 0.43 women.

    • DDx: Drugs (quinidine, procainamide, TCAs, phenothiazines), hypothermia, electrolyte abnormality, pentamidine, idiopathic.

• Axis: Normal if upright in I, F (or, more liberally, if -30 to +90).

• P waves: Best seen in II and VI.

  • Absent Ps: Atrial fibrillation (q.v. p. 205).

  • Inverted Ps in II, III, or F: Low atrial or junctional pacemaker.

  Figure 34. EKG axes.

• QRS waves:

  • Q wave = significant when more than 1 box wide or deep, or more than 1/3 of the following R wave. Normal in III, or small isolated Q in I, L, F, V4-V6. Q in III can also suggest PE.

  • Poor R-wave progression (PRWP): DDx = anterior MI, LBBB.

  • Too-good RWP (R in V1-V2 larger than in V3): Posterior MI, RV infarct, lateral MI, RBBB, RV hypertrophy, WPW.

  • LV hypertrophy: S in V1 + R in V5 >35 mm. LAD, wide QRS, and T slants down slowly and returns rapidly.

• ST segments: Compare voltages to TP segment, not PR.

  • ST elevation: Nl <1 mm limb leads; <2 mm chest.

    • DDx: Acute MI, LBBB, J point elevation (concave, upsloping ST in young people).

    • Persistent ST elevations: DDx: persistent ischemia, LV aneurysm, pericarditis (concave, widespread, or anterior).

  • ST depression: DDx: ischemia, digoxin (upsloping), exercise, strain, PE (especially lead II).

• T waves: Can be down in III, L, F, V1-V2. Brain injury can cause nonspecific T wave changes, but this is a diagnosis of exclusion.

  • Peaked (hyperacute) T waves: Ischemia, high K. Ts should be <5 mm in limb leads; <10 mm in chest leads.

  • T wave flattening: Ischemia, post MI, low K.

  • T wave inversion (TWI): Ischemia, post MI, BBB (should be in opposite direction), strain (biphasic and asymmetric in V5-V6), sometimes just from tachycardia. Normally inverted in R.

  • Pseudonormalized Ts: I.e., formerly inverted, now flat or upright. Suggests ischemia.

  • T wave axis: Should be <50 from QRS axis.

• U waves: Low K, low Mg.

E. Miscellaneous EKG syndromes

• Beta-blockers: Bradycardia, AV block.

• Bundle branch block (BBB): If QRS >0.12. Left BBBs can have fixed ST elevations not associated with MI, but always worry if the elevations change.

P.209

• Calcium:

  • Calcium channel blockers: Sinus arrest, AV block.

  • High Ca: Short QT, tachycardia.

  • Low Ca: Long QTc.

• Digoxin toxicity: Upsloping ST depressions, tachycardia, AV block, junctional rhythms, bradycardic junctional escape, V tach, V fib.

• Potassium:

  • High K: In sequence as K rises, see peaked T (esp. V2-V4), ST depression, decreased R waves, PR lengthening, flat P, wide QRS, long QT, torsades.

  • Low K: Flat T and U wave, ST depression, SVT, A fib, long QT.

• Pulmonary embolus: Often nonspecific sinus tachycardia, sometimes SI-QIII-TIII (big S in I, Q, and TWI in III), right axis deviation and right BBB.

F. Coronary artery dz

• Acute MI:

  • DDx of chest pain: Aortic dissection, peri- or myocarditis, PE, PTX, perforated ulcer, cholecystitis, pancreatitis, rupture of the esophagus, musculoskeletal pain.

  • Tests: See Rule Out MI Protocol, p. 209.

  • Rx: Emergency cardiology or medicine consult.

    • Reduce cardiac work:

      • But beware low BP if carotid dz, renovascular dz, aortic stenosis, RV infarct, big anterior MI, tamponade.

      • Nitroglycerine: SL and IV to increase coronary perfusion.

      • Beta-blocker: IV metoprolol.

        • Loading metoprolol: 5 mg IVP over 2 min 3 doses to lower heart rate, while SBP >100, HR >50, PR <0.24. Then 50 bid, and titrate up, with hold parameters.

        • Beware of PO BP drugs that cannot reverse fast.

        • Use cautiously in COPD, CHF, inferoposterior or big anterior MI.

      • Morphine: 2-5 mg IV. Reduces pain, preload. Watch BP.

    • Treat clot: Have pt. chew aspirin, IV heparin; consider lysis, angioplasty, bypass.

      • Heparin: For unstable angina, ST depressions, or chest pain with a baseline BBB.

      • Consider thrombolysis: For ST elevations. Absolute contraindications = recent surgery, stroke, GI or brain bleed.

• Complications of MI:

  • Arrhythmias: Cardiac monitor.

  • Hypotension: Suspect right ventricle infarct in anyone with hypotension during an inferoposterior MI.

  • Congestive heart failure: see p. 210.

• Rule Out MI Protocol:

  • Cardiology consult.

  • Drugs: Aspirin, heparin SC or IV (for unstable angina, needs several days of heparin to cool off), O₂, IV access, colace, sucralfate,

    P.210

    nitropaste q4h (see Admission Orders, p. 13, for doses; adjust if carotid dz or longstanding HTN).

  • Labs: CPK/troponin q8min 3, profile 7, PTT (bid if IV hep), Ca/Mg/phos, CBC, LFTs, lipids, drug levels, EKG qAM 3; consider echocardiogram, ETT with thallium (make pt. NPO after midnight) or Persantine- or adenosine-thallium scan (no caffeine or theophylline before scan).

  • Orders: Bed rest, check orthostatic BP, guaiac stools, I/Os, daily wts, low-salt and low-cholesterol diet, cardiac monitor (pt. may travel without), old chart to floor quickly.

• Chest pain orders: Check vitals, EKG during pain, nitroglycerine SL q5min 3 if SBP >90, O₂ 2 L/min, call resident, post-pain EKG. Consider Mylanta, morphine.

G. Preoperative cardiac evaluation

If pt. has any of the following CAD markers, consider pre-op cardiology consult: Age >70, prior angina or MI, prior CHF or ventricular arrhythmia, DM, positive stress test.

H. Congestive heart failure (CHF)

• Systolic failure:

  • H&P: Ask about SOB, check rales, JVP, edema.

  • DDx: Lung dz, noncardiac edema.

  • Rx: Goal = decreased preload.

    • Acute: Sit pt. up with legs dangling. Oxygen, morphine 2-5 mg IV, nitroglycerine SL or IV, furosemide 40 mg IV.

    • Severe: Consider digoxin, CPAP (helps LV pump, but bad if preload is low), dobutamine, intubation.

    • Orders: R/O MI orders, fluid restrict, low salt, daily weights.

    • Labs: Digoxin level, repeat K and CXR after diuretics, consider echocardiogram.

    • Drugs: Digoxin, furosemide, captopril (or isosorbide dinitrate + hydralazine).

  • Diastolic dysfunction: Goal is maintained preload, decreased afterload, and decreased contractility. Nitrates and diuretics are okay acutely, but try verapamil long term.

I. Blood pressure

• Hypertension:

  • Causes: MI, stroke, cerebral bleed, drug withdrawal or overdose, renal, endocrine, anxiety, aortic dissection or coarct, eclampsia.

  • Hypertensive crisis: Usually DBP >130 or SBP >250, with evidence of end-organ damage: heart, brain, renal, fundi.

    • Rx: Arterial line + IV nitroprusside or labetalol. see p. 172.

      • Contraindications to Nipride: Cerebral edema or coronary ischemia.

      • Avoid: SL nifedipine, which can drop BP too fast.

    • Time course: Decrease BP gradually, by 25% in the following intervals:

      • If cerebral hemorrhage, in 6-12 h.

      • If papilledema, in 3-6 h.

      • If CHF, LV failure, dissection, in 15 min.

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  • Antihypertensive drugs: Consider nifedipine 10 mg SL (danger of hypotension), or metoprolol 50 mg PO. For IV blood pressure control, see p. 172.

    • Aortic aneurysm: Use labetolol (lowers HR as well as BP) unless there is CHF.

    • CHF: Use ACE-I, diuretics, ₁-blockers. Avoid -blockers, diltiazem, verapamil.

    • CAD: Use -blockers, Ca channel blockers, ACE-I. Avoid diuretics, hydralazine.

    • Cerebral bleed or stroke: Use -blockers, then -blockers, then ACE-I.

    • COPD: Use Ca blockers, ACE-I, diuretics. Avoid -blockers.

    • DM: Use ACE-I, ₁-blockers, Ca blockers. Avoid -blockers, diuretics.

    • Diastolic dysfunction: Use -blockers or Ca blockers.

    • Heart block/bradycardia: Avoid -blockers, verapamil.

    • Hyperlipidemia: Use ₁-blockers, Ca blockers. Avoid -blockers, diuretics except indapamide.

    • Peripheral vascular dz: Use Ca blockers, ACE-I, diuretics. Avoid -blockers.

    • Renal failure: Use loop diuretics, Ca blockers, ACE-I (especially for DM or nephrotic syndrome, but use very cautiously). Avoid -blockers, K-sparing diuretics.

    • Sexual dysfunction: Use ACE-I, Ca blockers. Avoid -blockers, central -blockers, diuretics.

• Hypotension:

  • Causes: Heart rate, pump, or volume problem: drug effect, blood loss, dehydration, sepsis, third-spacing, adrenal insufficiency, tension PTX.

  • Tests: EKG, ABG, orthostatics, chem. 20, cultures, CXR.

  • Rx:

    • Trendelenburg position: Head of bed down 10 degrees. Of short-term benefit only; increases risk of aspiration.

    • If bradycardic: Correct rate before giving fluid or pressor.

    • Normal saline IV: Be careful if CHF.

    • Hold offending drugs.

    • Blood: For volume (be careful if CHF).

    • Oxygen: Especially if anemic (be careful if COPD, because of risk of CO₂ retention).

    • Take cultures: If febrile.

    • Pressors: Oral rx: fludrocortisone 0.1 mg qd or midodrine 10 mg tid. For IV pressors, see p. 172.

J. Cholesterol emboli syndrome

• Causes: Often after arterial catheterization, vascular surgery.

• Sx: Necrotic foot lesions, conjunctival petechiae, renal failure, depression and dementia, nausea and anorexia.

• Rx: Symptomatic.

K. Pulmonary artery catheter (Swann-Ganz catheter)

• Alternatives: Green dye cardiac output (requires arterial line and central line); noninvasive cardiac output (NICO) monitor, echocardiography, a better physical exam .

P.212

• Indications: Note there is no evidence that Swanns improve outcome. They may worsen it. They are useful for telling cause of shock (e.g., septic vs. cardiogenic); cause of pulmonary edema (e.g., cardiogenic vs. increased permeability); monitoring the effects of fluids, inotropes, pressors, afterload agents, and vasodilators; and optimizing oxygen transport.

• Relative contraindications: Coagulopathy, thrombocytopenia, endocardial pacemaker, severe pulmonary hypertension, ventricular arrhythmias, left bundle branch block (have external pacer ready in case of complete heart block), prosthetic right heart valve.

• Complications: Include these risks on the consent form.

  • During puncture: Arterial puncture, pneumo- or hemothorax, air embolism, nerve injury, thrombosis.

  • During advancement of catheter: Arrhythmias, cardiac perforation and tamponade, bundle branch block.

  • During maintenance of catheter: Pulmonary artery rupture, mural thrombus, infection, valve damage, pulmonary infarction.

• Normal values:

  • CVP: Central venous pressure, 5-8 mm Hg.

  • RA: Right atrial pressure, 0-8 mm Hg.

  • RV: Right ventricular pressure, (15-30)/(0-4) mm Hg.

  • PA: Pulmonary artery pressure, (15-30)/(6-12) mm Hg.

  • PCWP: Pulmonary capillary wedge pressure, 1-10 mm Hg.

  • LVP: Left ventricular pressure, (100-140)/(3-12) mm Hg.

  • CO: Cardiac output, 4-8 L/min (= HR stroke volume).

  • CI: Cardiac index, 2.5-4.2 L/min/m².

  • SVR: Systemic vascular resistance, 770-1500 dynes/sec/cm⁵.

  • PVR: Pulmonary vascular resistance, 20-120 dynes/sec/cm⁵.

  • MAP: Mean art. pressure, 70-105 mm Hg = 1/3 (SBP - DBP) + DBP.