What is the approach to interpreting electrocardiograms (EKGs) in Left Ventricular Assist Device (LVAD) patients when there is no native pacemaking activity?

EKG Interpretation in LVAD Patients

What the EKG Actually Represents

The EKG in LVAD patients continues to display native cardiac electrical activity—atrial depolarization, ventricular depolarization, and repolarization—regardless of the mechanical support provided by the device. The LVAD does not replace the heart's electrical conduction system; it only provides mechanical circulatory support by continuously pumping blood from the left ventricle 1, 2. The native pacemaking activity of the sinoatrial node and conduction through the AV node and His-Purkinje system remains intact and is what generates the electrical signals captured on the EKG 3, 2.

Key Principle: Electrical vs. Mechanical Function

• The LVAD provides mechanical support but does not alter intrinsic electrical conduction, so P waves, QRS complexes, and T waves continue to represent the heart's native electrical activity 3, 2
• Even during ventricular fibrillation, the EKG displays the chaotic electrical activity while the LVAD continues to provide forward flow mechanically 1
• The disconnect between electrical activity and mechanical output is critical: a patient can have organized electrical rhythm on EKG but inadequate LVAD flow, or conversely, adequate LVAD support despite arrhythmias 1, 2

Characteristic EKG Changes After LVAD Implantation

Post-LVAD EKGs demonstrate specific patterns that differ significantly from pre-implantation tracings, creating a new baseline that must be recognized to avoid misinterpretation. 3

The LVADS² Criteria (validated markers of LVAD presence):

• Low limb-lead voltage: Reduced QRS amplitude in leads I, II, III, aVR, aVL, aVF due to altered cardiac geometry and position 3
• Ventricular pacing patterns: May be present if the patient has a concurrent pacemaker or ICD 3
• Artifact (electrical): High-frequency electromagnetic interference from the LVAD motor creates device-specific noise patterns 3, 4, 5
• Duration of QRS >120 ms: Prolonged ventricular depolarization time 3
• ST-elevation in lateral leads: Persistent ST changes related to surgical implantation and altered ventricular mechanics 3
• Splintering of the QRS complex: Fragmented QRS morphology indicating altered conduction pathways 3

Device-Specific Electromagnetic Interference Patterns

Each LVAD model produces characteristic electromagnetic interference at frequencies related to its impeller rotational speed, which can be identified and filtered. 4

• HeartMate II and HeartMate 3: Prominent signal peak at the device-specific frequency of impeller rotation 4
• HeartMate 3: Additional peaks at frequencies corresponding to the artificial pulsatility rotational speeds 4
• HeartWare: Signal peak at a frequency equal to double the LVAD's set rotational speed 4
• Applying low-pass filters below the LVAD frequency peak or speed-specific bandstop filters significantly improves EKG clarity without compromising physiological high-frequency components 4

Practical Approach to EKG Interpretation

Step 1: Verify Technical Quality

• Recognize that 93% of technical alarms in LVAD patients are due to artifact, which creates false-positive arrhythmia detection 5
• Request filtered EKG tracings when available, as digital filtering dramatically improves waveform quality 4
• Use multiple leads to identify the clearest QRS morphology, as electromagnetic interference varies by lead 4

Step 2: Assess Native Rhythm

• Identify P waves to determine atrial activity (sinus rhythm, atrial fibrillation, atrial flutter) 1, 3
• Measure QRS duration and morphology to detect bundle branch blocks or ventricular pacing 3
• Evaluate for ventricular arrhythmias, which occur in approximately one-third of continuous-flow LVAD patients 1

Step 3: Correlate with Clinical Status

• Critical distinction: The EKG rhythm does not predict hemodynamic stability in LVAD patients—LVAD parameters (flow rate, power consumption, pulsatility index) provide the actual hemodynamic information 1, 6, 2
• Check LVAD flow rates, power consumption, and alarm status when interpreting any rhythm disturbance 1
• Assess blood pressure using Doppler ultrasound (target MAP 70-90 mmHg), as automated cuff measurements fail due to continuous flow 6
• Evaluate mental status and end-organ perfusion, not just the EKG rhythm 1

Step 4: Recognize High-Risk Arrhythmias

• Ventricular fibrillation: Even hemodynamically stable patients require electrical cardioversion (Class I recommendation), as prolonged VF causes progressive right heart failure despite LVAD support 1
• Sustained ventricular tachycardia: Initiate IV amiodarone (150 mg over 10 minutes, then 1 mg/min for 6 hours) as first-line therapy 1
• Bradycardia with pauses: A 4-second pause warrants continuous monitoring and consideration of permanent pacemaker, particularly if symptomatic 7

Common Pitfalls to Avoid

• Never assume hemodynamic collapse based solely on EKG rhythm: Patients with VF can be awake and conversant if LVAD function is adequate 1, 2
• Avoid chest compressions unless truly indicated: Inappropriate CPR can dislodge the LVAD cannula; verify loss of consciousness and inadequate LVAD flow before initiating compressions 1
• Do not rely on pulse palpation or auscultation: Peripheral pulses are typically absent or barely perceptible, and Korotkoff sounds are diminished with continuous-flow devices 6
• Recognize false arrhythmia alarms: 98% of audible arrhythmia alarms in LVAD patients are false positives due to electromagnetic interference and low-amplitude QRS complexes 5

Monitoring Recommendations

• Continuous EKG monitoring is Class I recommendation for all hospitalized LVAD patients, as arrhythmias provide insight into hemodynamics and may indicate need to adjust pump speed 1
• Monitoring must be performed by personnel trained in VAD care who understand the disconnect between electrical rhythm and mechanical support 1
• Serial EKGs help establish the patient's new post-LVAD baseline and detect interval changes 3

When to Escalate Care

• Sustained ventricular arrhythmias despite adequate LVAD function require cardiology consultation for antiarrhythmic therapy or ICD evaluation 1
• New-onset arrhythmias may indicate pump thrombosis, suction events, or right ventricular failure requiring immediate LVAD specialist involvement 2
• Any rhythm change accompanied by altered mental status, hypotension (MAP <70 mmHg), or LVAD alarms demands urgent multidisciplinary assessment 1, 6, 2