Heart Blocks nursing care: what to assess and what to do first

What it is and why it happens

A heart block is a delay or interruption in the electrical signal travelling from the atria to the ventricles through the AV node or His-Purkinje system. The degree tells you how much of that signal is getting through, and the degree is what should drive everything you do next.

First degree block is simply a PR interval longer than 0.20 seconds, with every atrial impulse still reaching the ventricles. It causes no symptoms and needs no treatment beyond monitoring — it's often an incidental finding on a routine ECG in an otherwise well patient, sometimes from digoxin, beta blockers, or a normal variant in a well-conditioned athlete.

Second degree splits into two patterns. Mobitz type I (Wenckebach) shows progressively lengthening PR intervals until a beat drops, usually from reversible AV node slowing. Mobitz type II drops beats without warning, with a constant PR interval beforehand, and reflects disease lower in the conduction system — it's the less stable of the two and carries a real risk of progressing to complete block.

Third degree block is complete AV dissociation. The atria and ventricles beat entirely independently of each other, with no relationship between P waves and QRS complexes. Cardiac output depends on a slow ventricular escape rhythm, and this degree requires a pacemaker.

How it presents — what you will actually see

First degree block presents as nothing. The patient is asymptomatic, and you'll only catch it on the monitor or a 12-lead ECG showing that stretched-out PR interval.

Mobitz I often causes mild, intermittent symptoms tied to the dropped beats — a skipped-beat sensation, brief lightheadedness — but the patient is frequently stable between episodes. Mobitz II is more concerning even when the ventricular rate looks adequate, because the drop is unpredictable and can extend without warning.

Third degree block presents as symptomatic bradycardia: a ventricular rate that can fall into the 20s to 40s, fatigue, syncope or near-syncope, confusion from reduced cerebral perfusion, and hypotension. Some patients compensate for a surprising length of time before decompensating sharply, so a stable-looking patient with this rhythm still needs urgent attention.

Nursing assessment priorities

Get a 12-lead ECG and confirm the degree and location of block rather than relying on rhythm strip alone — the PR interval pattern is what distinguishes Mobitz I from Mobitz II, and that distinction changes the urgency of your response.

Assess perfusion directly: level of consciousness, skin colour and temperature, capillary refill, and urine output if the patient is catheterised. A heart rate number alone doesn't tell you whether the patient is perfusing adequately.

Check vital signs and correlate the ventricular rate with blood pressure and symptoms — a rate of 45 tolerated well by one patient may cause syncope in another with poor cardiac reserve. Review the medication list for AV-nodal blocking agents such as digoxin, beta blockers, and calcium channel blockers, since these are common reversible contributors and often the first thing to hold. Continuous cardiac monitoring is mandatory for anything beyond first degree block, since Mobitz II and third degree can deteriorate with little warning.

Interventions and what to do first

First degree block: monitor and document. No intervention is required unless it's new and linked to a reversible cause like a medication, in which case that medication is reviewed with the prescriber.

Mobitz I: continue monitoring, hold AV-nodal blocking drugs if implicated, and treat only if the patient becomes symptomatic. Atropine can be used for symptomatic bradycardia here.

Mobitz II and third degree block: this is where the priority shifts. If the patient is symptomatic — hypotensive, altered, or poorly perfused — the first action is to prepare for transcutaneous pacing and have atropine and emergency equipment at the bedside, following ACLS bradycardia protocol. Atropine is used with caution in Mobitz II and is generally ineffective in third degree block, since the escape rhythm originates below the level atropine acts on. Third degree block ultimately needs a permanent pacemaker, and a temporary transvenous or transcutaneous pacer bridges the patient until that's placed.

Complications to watch for

The main risk with Mobitz II is unpredictable progression to third degree block, so any patient with this rhythm needs continuous monitoring even while appearing stable — don't be reassured by a normal-looking rate between dropped beats.

Watch for signs of low cardiac output as block worsens: falling blood pressure, cool and mottled skin, decreasing urine output, and worsening mental status. In third degree block, prolonged inadequate perfusion can precipitate syncope with fall injury, heart failure, or cardiac arrest if the escape rhythm fails altogether. Also monitor for pacemaker-related complications once one is placed — lead displacement, failure to capture or sense, and insertion-site infection.

Patient teaching before discharge

Patients going home with first or asymptomatic Mobitz I block should understand what the diagnosis means, which medications to avoid or take exactly as prescribed if an AV-nodal agent was implicated, and when to seek care — new dizziness, fainting, or a noticeably slower pulse.

Patients discharged with a pacemaker for higher-degree block need education on site care and signs of infection, activity restrictions during initial healing, avoiding strong electromagnetic interference sources, and carrying their device identification card. Teach them to check and report their pulse if instructed, recognise symptoms of pacemaker malfunction such as recurrent dizziness or syncope, and keep scheduled device checks — these confirm the pacemaker is capturing and sensing correctly over time.