Compare conditions

Put any two — or three — conditions side by side, adult or pediatric, to spot the look-alike differences fast, row by row.

AV block

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In one line

·The electrical signal from the top chambers gets delayed or blocked before it reaches the bottom chambers.

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Normal physiology

·The AV node is a cluster of specialized cells between the atria and ventricles that slows down the electrical signal just long enough for the ventricles to fill with blood before they squeeze.

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What goes wrong

·AV block happens when the AV node or the wiring below it gets damaged, poisoned, inflamed, or was never built right in the first place.

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Hallmark signs

·Slow heart rate (bradycardia)
·Feeling dizzy or lightheaded
·Feeling very tired or weak
·Shortness of breath
·Chest discomfort or pressure
·Fainting or near-fainting (syncope)
·Confusion or trouble thinking clearly
·Long PR interval, skipped beats, or AV dissociation on electrocardiogram (ECG)

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Red flags · escalate now

·Fainting or near-fainting (syncope)
·Sudden severe dizziness or confusion
·Chest pain or pressure that doesn't go away
·Very slow heart rate (under 40 beats per minute) with symptoms
·Shortness of breath at rest or worsening quickly

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Workup

·12-lead electrocardiogram (ECG)
·Continuous cardiac monitoring (telemetry)
·Serum electrolytes — potassium, magnesium, calcium
·Troponin I or T
·Lyme disease serology (ELISA, then Western blot if positive)
·Medication review — check for beta-blockers, calcium channel blockers (diltiazem, verapamil), digoxin, antiarrhythmics (amiodarone, sotalol)
·Echocardiogram (ultrasound of the heart)
·Chest X-ray

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Treatment

·Atropine 0.5–1 mg IV push (can repeat every 3–5 minutes, max 3 mg total) for symptomatic AV block at or above the AV node level
·Transcutaneous pacing (electrical pads on the chest delivering pacing pulses) or transvenous temporary pacemaker wire inserted through a vein into the right ventricle
·Permanent pacemaker implantation (a small device placed under the skin with wires threaded into the heart)
·Restore blood flow to the right coronary artery (RCA) with percutaneous coronary intervention (PCI) or thrombolytics if AV block is caused by acute inferior MI
·Stop or reduce the dose of AV-blocking drugs (beta-blockers like metoprolol, calcium channel blockers like diltiazem or verapamil, digoxin, amiodarone)
·IV ceftriaxone 2 g daily for 14–21 days if AV block is caused by Lyme carditis (confirmed by positive Lyme serology)
·Correct electrolyte abnormalities — give IV insulin and glucose or sodium polystyrene sulfonate (Kayexalate) for high potassium (hyperkalemia), IV magnesium sulfate for low magnesium, IV fluids and calcitonin or bisphosphonates for high calcium

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NCLEX trap

·The type (degree) of AV block matters a lot. First-degree block usually needs nothing. Mobitz II or complete (third-degree) block needs a pacemaker, not just medicine. Atropine only helps if the problem is in the AV node itself, not if the problem is lower down in the bundle branches (the wires below the node).
·You must get an ECG right away. A rate of 50 can hide dangerous AV block underneath. The ECG tells you which degree you are dealing with. Mobitz II or complete block can suddenly get much worse — people can faint or their heart can stop. Never wait.
·AV block can be quiet until it suddenly is not. Complete block or Mobitz II can cause fainting or even cardiac arrest (the heart stops pumping) without warning. You decide what to do based on the ECG pattern, not just how the patient feels right now.
·First-degree and Wenckebach (Mobitz I) do not need pacing — you just watch them. Only Mobitz II and complete AV block with symptoms (dizziness, fainting, low blood pressure) get a pacemaker. Look at the pattern first, then decide.
·It depends on what caused the block and how bad it is. Block caused by medicines (like beta-blockers or digoxin) may go away when you stop the drug. Block after a heart attack often gets better in a few days as swelling goes down. Only block that stays and causes symptoms needs a permanent pacemaker.
·Blood pressure can be normal at first, then drop suddenly if more beats are lost or the backup (escape) rhythm fails. Check the trend, not just one number. A patient with AV block can crash fast — pressure can fall, the brain can stop getting blood, and the person can faint or worse.

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