3 Dysrhythmia Recognition
Learn a consistent approach to rhythm-strip interpretation, recognize common conduction and atrial rhythm patterns, and connect ECG findings to patient stability and appropriate escalation.
A consistent rhythm-reading approach
Use the same sequence for every rhythm strip: assess the ventricular rate and regularity, identify P waves, compare P waves with QRS complexes, and measure the PR and QRS intervals. Then assess the patient’s responsiveness, pulse, blood pressure, symptoms, and perfusion.
A monitor pattern alone does not establish how urgently to intervene. Confirm the rhythm and base the response on the patient’s condition. Continue assessment and follow local protocols; escalate abnormal or concerning findings.
Slow sinus rhythm and first-degree block
A regular rhythm at beats/min with an upright P wave before each narrow QRS and a consistent supports sinus origin. If the patient is alert and denies symptoms, assess and continue to monitor rather than treating the slow rate alone as proof of instability.
A of seconds that remains constant, with a P wave before every QRS, is a . In this pattern, the is prolonged—greater than seconds—but every P wave is conducted to a QRS complex.
Second-degree AV blocks
In , the becomes progressively longer until a P wave is not followed by a QRS complex; the sequence then repeats. This pattern distinguishes it from a constant prolonged with a QRS after every P wave.
In , P waves are regular and QRS complexes are intermittently dropped, while the PR intervals before conducted beats remain constant. Because can progress to more serious block, promptly escalate and assess the patient rather than relying on the strip alone.
Complete heart block
In , P waves are regular and the QRS rhythm is slower and regular, but the atrial and ventricular activity occur independently with no consistent PR relationship. This is complete AV dissociation.
Assess stability and promptly escalate care. Clinically significant bradycardia may require urgent treatment.
and flutter
is suggested by an irregularly irregular rhythm without distinct P waves before the QRS complexes.
is suggested by repetitive, sawtooth-like atrial waves. When several atrial waves occur for each QRS complex in a consistent relationship, the pattern indicates a conduction ratio.
Tachycardia and patient stability
A sudden-onset, regular rhythm at beats/min with narrow QRS complexes fits a category, such as an SVT pattern. If the patient is alert, has a palpable pulse, and has stable blood pressure, continue assessment and follow local protocols. If the patient becomes unstable, emergency treatment is indicated.
A rapid, regular wide-complex rhythm requires urgent assessment. For example, a rhythm at beats/min with a palpable pulse, severe hypotension, and altered mental status indicates instability. Activate emergency assistance and prepare for prompt under the applicable protocol. Do not treat the patient as stable merely because a pulse is present, or give an AV-nodal blocking medication without further evaluation.
If a patient with a rapid wide-complex rhythm loses a pulse, activate the cardiac-arrest response and follow the appropriate resuscitation algorithm.