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The timing of ventricular premature complexes initiating chronic ventricular tachycardia
Insights
The prematurity index (PI) of ventricular premature complexes (VPCs) initiating ventricular tachycardia (VT) is typically longer than isolated VPCs in individual patients. VT rate is predictable from the first interectopic interval, offering mechanistic insights.
Area of Science:
- Cardiology
- Electrophysiology
- Medical Science
Background:
- Ventricular premature complexes (VPCs) can initiate ventricular tachycardia (VT).
- The prematurity index (PI) is a measure of VPC timing relative to the preceding R-R interval.
- Understanding VPCs that trigger VT is crucial for arrhythmia management.
Purpose of the Study:
- To investigate the relationship between the prematurity index (PI) of isolated VPCs and those initiating ventricular tachycardia (VT).
- To determine if the PI differs significantly between isolated VPCs and VPCs triggering VT within individual patients.
- To explore predictors of VT rate and regularity.
Main Methods:
- Analysis of 496 VT episodes in 122 patients using 24-hour ambulatory ECG recordings.
- Calculation of the prematurity index (PI) for isolated VPCs and VPCs initiating VT.
- Comparison of PI values, coupling intervals, and interectopic intervals between different types of VPCs and VT episodes.
Main Results:
- The PI of VPCs initiating VT was significantly longer than that of isolated VPCs in individual patients (P < 0.01).
- The coupling interval of the first VT complex was longer than the first interectopic interval (VT1-VT2) in 72% of patients.
- VT1-VT2 interval strongly correlated with the average R-R interval during VT (r = 0.75, P < 0.001).
- Irregular VT was associated with shorter VT duration (P < 0.05).
Conclusions:
- For individual patients, VPCs triggering VT tend to have a longer PI than isolated VPCs.
- The rate of VT is generally predictable from the first interectopic interval.
- These findings have potential mechanistic implications for understanding VT initiation and progression.
Abstract:
Prematurity index (PI), defined as the ratio of the coupling to QT intervals of isolated ventricular premature complexes (VPC) and those initiating ventricular tachycardia (VT) on 24-hour ambulatory ECG recording, was examined in 496 episodes of VT occurring in 122 patients. The PI of VPC initiating VT was less than 1 in only 62 (13%) of the VT episodes and occurred in 14 patients. Although the range of PI was similar for isolated VPC and those initiating VT, for individual patients the PI of VPC initiating VT was significantly longer than the PI of isolated VPC (P less than 0.01). This relationship was not affected by age, sex, presence of absence of heart disease, or drug therapy. The coupling interval of the first VT complex was longer than the first interectopic interval of the VT (VT1-VT2) in 88 (72%) patients; and, the VT1-VT2 interval correlated strongly with the average R-R during VT (r = 0.75), (p less than 0.001). The VT was irregular in 48 patients with 300 episodes of VT. Irregularity of the VT was significantly associated with shorter duration of VT (p less than 0.05). These results show that, for individual patients, the PI of VPC initiating VT tends to be longer than that of isolated VPC, and that the rate of VT is usually predictable from the duration of the first interectopic interval of the VT. These results may have mechanistic implications.