Early Detection of Pacing-Induced Cardiomyopathy:
Best Echocardiographic & Advanced Imaging Parameters

The Diagnostic Challenge: Why EF Is Not Enough

Pacing-induced cardiomyopathy (PICM) is conventionally defined as a new-onset reduction in left ventricular ejection fraction (LVEF) ≥10% resulting in an EF below 50%, attributable to chronic right ventricular (RV) pacing in the absence of other identifiable causes. While this definition is clinically operational, it represents a late-stage endpoint. By the time LVEF drops below the diagnostic threshold, significant myocardial remodeling—eccentric LV dilation, interstitial fibrosis, diastolic dysfunction, and mitral regurgitation—may already be established.

PICM affects approximately 6–25% of patients with high RV pacing burden, with a real-world incidence of 10–13% in contemporary leadless pacemaker cohorts. The critical unmet clinical need is pre-symptomatic detection, enabling timely upgrade to conduction system pacing (His-bundle pacing or LBBAP) or cardiac resynchronization therapy before irreversible structural damage occurs.

PICM Incidence in Leadless Pacemaker Patients

The introduction of leadless pacemakers (Micra TPS, Micra AV, Abbott Aveir VR) eliminated pocket- and lead-related complications but did not eliminate the risk of PICM. Several contemporary studies illuminate the scope of this problem:

A key anatomical modifier is implant position. Mid/high septal placement of the leadless device appears more favorable than apical septal positioning, though residual confounding from anatomic complexity—such as tricuspid regurgitation or RV dilation influencing implant site selection—cannot be fully excluded.

Importantly, predictors of PICM in leadless pacemaker patients mirror those in transvenous pacemaker patients: high pacing burden, wide native and paced QRS, prior congestive heart failure, chronic kidney disease, and a relatively lower baseline LVEF (even within the normal range).

1. Global Longitudinal Strain (GLS) — The Premier Early Marker

Global Longitudinal Strain, measured by 2D speckle-tracking echocardiography (STE), is the most extensively validated early imaging marker for PICM. Its advantages over LVEF are threefold: it detects subclinical myocardial dysfunction, it is sensitive to longitudinal fiber derangement (the dominant mechanism of RV pacing injury), and it changes before volumetric remodeling is detectable.

Pre-Implant GLS as a Risk Stratifier

A pre-implant GLS value that is less negative than expected for a given preserved EF signals occult myocardial vulnerability. In a retrospective study of patients with complete atrioventricular block (CAVB) implanted with dual-chamber pacemakers, a pre-implant LV GLS cutoff of less than −20.7% predicted PICM with a sensitivity of 81.3% and specificity of 58.0%, remaining an independent predictor on multivariate analysis alongside native QRS duration (HR 1.27; 95% CI 1.009–1.492; p=0.04).

The clinical implication is direct: a patient with LVEF 60% and GLS −16% carries substantially higher PICM risk than one with LVEF 60% and GLS −22%, even though both are "preserved." This patient should be considered for conduction system pacing de novo if technically feasible—particularly relevant for patients with complete heart block and anticipated near-100% pacing burden.

Post-Implant GLS at 1 Week

Early post-pacing GLS deterioration is a powerful predictor of later PICM. In a prospective study of 175 consecutive patients undergoing permanent pacemaker implantation, a reduction in baseline GLS of 15% or more at 1 week post-implantation was significantly associated with subsequent development of pacing-induced ventricular dysfunction and PICM (p <0.001). Critically, this GLS drop preceded any measurable LVEF change.

Post-Implant GLS at 1 Month

The PAVD study demonstrated that one-month GLS was significantly lower in patients who ultimately developed pacing-induced LV dysfunction versus those who did not (−12.6 vs. −16.4; p=0.022). GLS declined progressively from baseline in future PICM patients, while remaining stable in non-PICM patients.

2. Strain-Derived Dyssynchrony Indices

Dyssynchrony—the temporal and spatial discoordination of LV contraction caused by the abnormal activation sequence of RV pacing—is the central pathophysiologic mechanism of PICM. Multiple speckle-tracking-derived parameters quantify this discoordination:

Time-to-Peak Strain Standard Deviation (TPS-SD)

TPS-SD quantifies the dispersion of time-to-peak longitudinal strain across LV segments. An elevated TPS-SD (≥75 ms is considered pathological) reflects heterogeneous contraction timing—early activation and contraction of septal segments followed by delayed lateral wall activation. In the polar plot strain map, this manifests as a "butterfly" or asymmetric pattern with early-peaking septal strain and late-peaking lateral strain. TPS-SD is considered one of the most sensitive dyssynchrony indices for PICM surveillance in speckle-tracking protocols.

Peak Systolic Dispersion (PSD)

PSD represents the standard deviation of time intervals to peak systolic strain across all 16 LV segments. It provides a more accurate and sensitive index of early LV systolic function than visual dyssynchrony assessment and is increasingly incorporated into echocardiographic protocols for pacemaker follow-up, particularly in the context of conduction system pacing evaluation.

Mechanical Propagation Delay (MPD)

MPD measures the delay between earliest and latest regional peak strain, reflecting the full extent of interventricular and intraventricular mechanical discoordination. Elevated MPD in a paced patient with preserved EF should prompt consideration of early intervention or upgrade.

Septal-to-Posterior Wall Motion Delay (SPWMD)

SPWMD, obtained by M-mode echocardiography from the parasternal short-axis view at the papillary muscle level, is one of the earliest validated dyssynchrony parameters. A threshold of >130 ms indicates LV dyssynchrony, and its presence after pacemaker implantation predicts PICM development over subsequent years—even in patients with normal LVEF at the time of measurement.

3. Visual Dyssynchrony Signs: Septal Flash and Apical Rocking

On standard 2D transthoracic echocardiography, RV pacing characteristically produces two visually identifiable dyssynchrony signs: septal flash (early systolic inward septal motion followed by outward rebound) and apical rocking (lateral displacement of the cardiac apex during systole). Both are direct consequences of the abnormal activation sequence generated by apical or apical-septal RV pacing.

While qualitative rather than quantitative, the presence of prominent septal flash or apical rocking in a pacemaker-dependent patient should trigger formal strain analysis and closer surveillance intervals. Their persistence on repeat imaging—particularly if SPWMD or TPS-SD is elevated—strengthens the case for conduction system pacing upgrade.

4. Interventricular Mechanical Delay (IVMD)

IVMD, measured by tissue Doppler or speckle-tracking as the time difference between LV and RV peak systolic motion, directly quantifies interventricular dyssynchrony. In a reported case of PICM after leadless pacemaker implantation, IVMD was documented at 42 ms at presentation with heart failure and LVEF of 40%—significantly elevated from pre-implant baseline. After restoration of native rhythm, IVMD normalized to 7 ms alongside improvement in LVEF and GLS, confirming the causative relationship between RV pacing and LV dysfunction.

IVMD thresholds >40 ms are generally considered abnormal in the context of paced patients. Serial IVMD measurement provides a quantitative, reproducible, and physiologically interpretable index of mechanical dyssynchrony for PICM surveillance.

5. Three-Dimensional Echocardiography (3DE)

Three-dimensional echocardiography offers advantages over 2D biplane methods in PICM surveillance through greater volumetric accuracy and more comprehensive dyssynchrony assessment:

Full-volume 3DE allows precise measurement of LV end-diastolic and end-systolic volumes without geometric assumptions—critical in the asymmetrically remodeled, dyssynchronous LV. Studies have shown that 3DE detects early volumetric changes associated with PICM before they reach significance on 2D biplane calculations. Additionally, 3D speckle-tracking strain analysis provides simultaneous assessment of longitudinal, circumferential, and radial strain across all LV segments in a single acquisition, offering a more complete dyssynchrony fingerprint. This approach also provides superior lead/device localization within the interventricular septum for patients being considered for upgrade procedures.

6. Myocardial Work Indices

Myocardial work analysis—derived from the pressure-strain loop (combining non-invasive LV pressure estimation via brachial cuff with regional strain data)—provides a load-adjusted assessment of myocardial function that is increasingly important in PICM evaluation:

In paced patients, wasted myocardial work (Mw-waste) is elevated because early-contracting septal segments perform work against a not-yet-loaded aortic valve, while late-contracting lateral segments bear a disproportionate mechanical burden. Global Work Efficiency (GWE), the ratio of constructive to total myocardial work, falls below normal values in established PICM but may decline detectably earlier than GLS in some patients. Myocardial work analysis thus provides a physiologically richer PICM detection framework than strain alone—particularly useful in patients with arterial hypertension or other conditions that affect afterload and confound conventional strain interpretation.

7. Diastolic Dysfunction and Left Atrial Remodeling

PICM encompasses not only the classical LV systolic dysfunction phenotype (LVEF <50%) but also a HFpEF phenotype driven by diastolic dysfunction, elevated filling pressures, and LA remodeling. This form may go undetected if surveillance focuses exclusively on LVEF and systolic strain parameters.

Key diastolic surveillance parameters in patients with high RV pacing burden include: E/e' ratio (septal and lateral); LA volume index (LAVI) serial trending; peak tricuspid regurgitation velocity (as a surrogate for RV systolic pressure); and the presence of restrictive or pseudonormal filling patterns. Progressive LA enlargement in the absence of atrial fibrillation or significant mitral valve disease should be interpreted as a marker of chronically elevated LV filling pressures and potential early PICM—even with preserved EF.

8. Right Ventricular Function: An Underrecognized Target

Emerging evidence identifies pacing-induced RV cardiomyopathy as a distinct entity that may develop independently of—or concurrently with—LV cardiomyopathy. In a recently published Circulation: Arrhythmia & Electrophysiology study, each 1 cm/s reduction in baseline RV S' (tissue Doppler-derived peak systolic velocity of the RV free wall) was associated with earlier onset of pacing-induced RV cardiomyopathy (HR 0.78; p=0.02). Patients who developed RV cardiomyopathy were more likely to have received leadless devices (21% vs. 6% in those without RV cardiomyopathy).

RV function parameters warranting serial monitoring include: TAPSE (tricuspid annular plane systolic excursion); RV S' by tissue Doppler; RV free-wall longitudinal strain by speckle tracking; and RV end-diastolic area indexed to body surface area.

Evidence Summary Table: Echocardiographic Parameters for PICM Detection

Evidence-Informed Surveillance Protocol

No society guideline currently mandates a specific echocardiographic surveillance schedule for leadless pacemaker patients beyond the standard 1-year post-implant echo. However, given the 10–13% PICM incidence and the evidence that early GLS monitoring identifies patients before EF decline, the following protocol reflects best available evidence for patients with significant (≥40%) RV pacing burden:

Clinical Implications for Upgrade Decision-Making

The 2023 HRS/APHRS/LAHRS Guideline on Cardiac Physiologic Pacing for the Avoidance and Mitigation of Heart Failure provides Class I indication for upgrade to conduction system pacing or biventricular pacing in patients with PICM (EF <50% with high pacing burden). However, the imaging evidence reviewed here supports a more proactive approach: patients with GLS decline, elevated dyssynchrony indices, progressive diastolic dysfunction, or LA remodeling despite preserved EF represent a pre-PICM substrate warranting early multidisciplinary discussion about upgrade candidacy.

For patients with leadless pacemakers specifically, upgrade to LBBAP involves a hybrid strategy: retention of the leadless device (either as backup or programmed to standby) with addition of a transvenous LBBAP lead and CRT-capable generator. Echocardiographic response criteria post-upgrade—LV reverse remodeling, GLS improvement, and diastolic parameter normalization—are the same imaging benchmarks used to evaluate CRT response.

Conclusion

Pacing-induced cardiomyopathy affects approximately 10–13% of leadless pacemaker patients—a rate equivalent to transvenous systems—and its early detection depends on advanced echocardiographic parameters rather than LVEF alone. Global Longitudinal Strain is the most evidence-supported parameter, offering pre-implant risk stratification and early post-implant detection before volumetric remodeling occurs. Dyssynchrony indices including TPS-SD, SPWMD, and IVMD provide complementary mechanistic information. Emerging tools—3D echocardiography, myocardial work analysis, and RV strain—complete the imaging arsenal for comprehensive PICM surveillance.

For clinicians managing pacemaker-dependent patients with high RV pacing burden, integrating GLS-based surveillance into routine follow-up is now supported by a robust and growing evidence base, and represents the most rational strategy to identify candidates for early upgrade to conduction system pacing before irreversible structural damage occurs.