Radiotherapy Dose as a Predictor of Outcomes Following Cardiac Radioablation for High-risk Refractory VT

PURPOSE/OBJECTIVE(S)

Cardiac radioablation (CRA) is an emerging treatment for high-risk refractory ventricular tachycardia (VT). Despite a fixed prescription dose to the planning target volume (PTV) there is still considerable heterogeneity in the radiotherapy dose distribution due to planning technique, proximity to organs at risk, and radiation oncologist preference. The hypothesis is that plans with an inherently "hotter" internal dose to the PTV may lead to improved VT outcomes.

MATERIALS/METHODS

Single-center, IRB-approved retrospective case series of patients with refractory VT who had failed at least one prior CA (or were unfit for CA) treated with CRA. All patients were treated with a single fraction of 25 Gy prescribed to the PTV. Maximum dose to PTV was collected from each plan and stratified as high vs low above and below the median. Maximum dose was defined as the highest dose delivered to the "hottest" 0.035 cc of the PTV to avoid known variability in reporting of dose to single voxels within the treatment planning system. Rates of survival (OS), freedom from shock and/or storm (FFSS), and freedom from death, shock, and/or storm (FFDSS) were collected, and stratified by maximum dose to the PTV. Formal statistical comparisons were not performed due to limited patient numbers.

RESULTS

From 2015-2020, 22 patients were treated with CRA (18 with prior CA, 4 unfit for CA) for high-risk refractory VT. Median age was 64.5 years (range, 49-84), and 90.9% were male. 50% had ICM, with a median NYHA class of 3 (range, 1-4) and median EF of 25% (range, 15-58%). Median follow-up was 31.3 months. 2-year OS was 54.5%, FFSS was 42.4%, and FFDSS was 27.3%. Median maximum dose to the PTV was 42.2 Gy (range, 29.2-45.8 Gy). PTV maximum dose (high vs low) discriminated 2-year OS (63.6% vs 45.5%), FFSS (50% vs 30%) and FFDSS (36.4% vs 18.2%). For all endpoints, Kaplan-Meier curves overlapped for the first 6 months, and then diverged.

CONCLUSION

In patients with high-risk refractory VT treated with CRA, survival and VT outcomes were similar between both groups out to 6 months, with improved OS and VT control noted after that with higher maximum doses. With a prescription dose of 25 Gy to the PTV, adjusting planning parameters to maintain maximum doses > 42 Gy may improve durable outcomes and requires validation in a larger cohort.

Transformation of computerized electrocardiogram data into novel means to differentiate wide complex tachycardias

Background

Accurate automated wide QRS complex tachycardia (WCT) discrimination between ventricular tachycardia (VT) and supraventricular wide complex tachycardia (SWCT) can be accomplished using novel calculations derived from computerized electrocardiogram (ECG) data from paired WCT and baseline ECGs.

Purpose

Our aim was to develop and trial novel WCT discrimination approaches for WCT patients with and without a corresponding baseline ECG. Central to this analysis was the creation and use of a novel parameter (i.e., percent monophasic time-voltage area [PMonoTVA] [%]) that may be derived from computerized ECG measurements present on the WCT ECG alone.

Methods

In a two-part study, we derived and tested WCT differentiation models comprised of novel and previously established parameters formulated from computerized data of paired WCT and baseline ECGs. In Part 1, novel and established parameters generated from WCT and baseline ECG data were used to derive, validate, and compare five different binary classification models: (i) logistic regression [LR], (ii) artificial neural network [ANN], (iii) Random Forests [RF], (iv) support vector machine [SVM], and (v) ensemble learning (EL). In Part 2, two unique LR models were derived, validated, and compared using parameters generated from computerized data of the (i) WCT ECG alone (i.e., Solo Model) and (ii) paired WCT and baseline ECGs (i.e., Paired Model).

Results

In Part 1, among 103 patients with VT or SWCT diagnoses established from corroborating electrophysiology studies or intra-cardiac device recordings, favorable diagnostic performance was achieved by all modeling technique subtypes: LR (area under the receiver operating characteristic curve [AUC] 0.95), ANN (AUC 0.91), RF (AUC 0.97), SVM (AUC 0.98), and EL (AUC 0.97). In Part 2, among 235 patients with a VT or SWCT diagnosis established with (Gold Standard cohort) or without (Non-Gold Standard cohort) a corroborating electrophysiology procedure or intra-cardiac device recording, favorable diagnostic performance was achieved by the Solo Model (AUC 0.86) and Paired Model (AUC 0.95) (Table).

Conclusion

Accurate WCT discrimination may be accomplished using novel parameters derived from computerized data of the WCT ECG alone and paired WCT and baseline ECGs.

Funding Acknowledgement

Type of funding sources: Public grant(s) – National budget only. Main funding source(s): National Institute of Health