6 Dysrhythmias
Learn to interpret common dysrhythmias, assess how they affect perfusion, and select an appropriately urgent initial response.
Start with the patient
A is a change in the heart’s rate, rhythm, or electrical conduction. Rhythm recognition helps identify a pattern, but the patient’s condition determines urgency. Assess the patient, confirm whether a pulse is present, and look for poor perfusion before responding to the monitor.
Interpret rhythm strips systematically
Use the same sequence to interpret each rhythm strip:
Rate: Estimate the ventricular rate. For a regular rhythm on standard ECG paper, divide by the number of large boxes between R waves. For an irregular rhythm, count QRS complexes in and multiply by .
Regularity: Compare R–R intervals, then compare P–P intervals if P waves are present.
P waves: Check whether they are present and consistent, and whether each P wave precedes a QRS.
PR interval: Check whether it is consistent. A normal PR interval is approximately .
QRS duration: Decide whether the complex is narrow or wide. A QRS duration of or more is wide.
Patient assessment: Check pulse, blood pressure, mental status, symptoms, oxygenation, and signs of shock or acute heart failure.
ECG findings help identify rhythm patterns, but interpret them alongside the patient’s clinical status.
Recognize slow and atrial rhythms
has a regular rhythm, a normal P wave before each QRS, and a rate below . It may be normal or medication-related. Treat when symptoms or poor perfusion are present, not solely because the rate is slow.
usually has irregularly irregular R–R intervals and no distinct, consistent P waves. Assess the rate and perfusion. increases stroke risk, and anticoagulation decisions depend on individual thromboembolic risk. has repeating sawtooth flutter waves; its ventricular rhythm may be regular or variable. Assess hemodynamic stability and ventricular rate, and consider stroke-risk assessment.
Recognize tachycardias and ventricular beats
is usually a regular, narrow-complex tachycardia, and P waves may be hard to see. If the patient is stable and the rhythm is regular, vagal maneuvers and, when indicated, adenosine may be used under protocol or prescription.
Premature ventricular complexes (PVCs) appear as early, wide QRS complexes without a preceding normal P wave and are often followed by a pause. Assess symptoms and frequency. Look for possible triggers such as ischemia, hypoxia, or electrolyte abnormalities.
is usually a regular, wide-complex tachycardia. Check for a pulse immediately: pulseless VT is a cardiac-arrest rhythm, while unstable VT with a pulse requires urgent treatment.
Recognize cardiac-arrest rhythms and
appears as disorganized electrical activity without identifiable organized QRS complexes. If the patient has no pulse, treat this as cardiac arrest: activate the emergency response, begin CPR, and defibrillate as soon as a defibrillator is available.
patterns include:
First degree: Prolonged PR interval.
Mobitz I: The PR interval lengthens progressively until a QRS is dropped, then the pattern repeats.
Mobitz II: A QRS is intermittently dropped without progressive PR lengthening.
Third degree: P waves and QRS complexes have no consistent relationship.
Assess patients with for symptoms and instability. High-grade blocks can require urgent pacing and expert care.
Take initial nursing actions
Begin by assessing responsiveness, breathing, and pulse; a rhythm on the monitor does not by itself establish the patient’s condition. If the patient is unstable, activate the emergency response system, summon help, and prepare for resuscitation or urgent intervention.
Maintain a patent airway and support breathing as needed. Give oxygen if the patient is hypoxemic rather than routinely for every . Apply continuous cardiac monitoring, obtain blood pressure and oxygen saturation, establish IV access as appropriate, and obtain a 12-lead ECG when feasible without delaying urgent care.
Notify the responsible clinician and report the rhythm, rate, pulse status, symptoms, vital signs, and relevant changes. Anticipate evaluation for reversible causes, including ischemia, hypoxia, medication effects, and electrolyte abnormalities. Follow local protocols and scope of practice.
Respond to unstable tachycardia
Signs of cardiopulmonary compromise include hypotension, acutely altered mental status, shock, ischemic chest discomfort, and acute heart failure. Persistent tachyarrhythmia with these signs calls for urgent by trained clinicians. Sedation is used when feasible without delaying emergency treatment.
For example, a patient with a rapid, regular, narrow-complex rhythm who is confused and hypotensive is unstable. Activate emergency assistance and prepare for rather than delaying care for a prolonged ECG or nonessential steps.
Respond to bradycardia with a pulse
When bradycardia with a pulse is causing cardiopulmonary compromise, support the patient and prepare for treatment under the current resuscitation algorithm. The algorithm includes atropine and, if it is ineffective, transcutaneous pacing and/or a dopamine or epinephrine infusion. Expert consultation and transvenous pacing may also be considered.
A slow but organized rhythm does not automatically require treatment. For example, a patient with a regular rhythm at , a consistent P wave before each narrow QRS, no symptoms, and stable blood pressure should be assessed and monitored; treatment depends on clinical status, not rate alone.
Treat pulseless VT and VF as cardiac arrest
For pulseless VT or VF, activate the code response, begin high-quality CPR, and use a defibrillator as soon as available. Both rhythms are shockable. Resume CPR immediately after a shock and follow the current cardiac-arrest algorithm.
A chaotic rhythm with no organized QRS complexes and no pulse calls for immediate CPR, emergency activation, and preparation to defibrillate. Do not wait for the rhythm to become organized or delay care to obtain a 12-lead ECG.
Use clinical judgment and follow safety requirements
Electrical therapy, antiarrhythmic drugs, and emergency medication doses require appropriate training, orders or approved protocols, and facility policy. Prepare equipment, support the patient, monitor the response, and document care. Do not delay emergency escalation while attempting prolonged rhythm analysis.
A wide-complex tachycardia with a pulse requires assessment for cardiopulmonary compromise before deciding on the next intervention. New chest pressure with frequent PVCs also calls for assessment of the patient and vital signs, prompt notification of the responsible clinician, and preparation for further evaluation.