Relationship between episodes of unsustained VTs detected early after an ICD implant and subsequent monomorphic VTs causing appropriate therapy

Introduction

Non-sustained ventricular tachycardias (NSVT) are observed frequently among ICD patients with left ventricular dysfunction (LVD).

Purpose

To analyze the relationship between episodes of NSVTs and monomorphic VTs (MVTs) that subsequently cause appropriate therapies.

Methods

416 ICD patients with LVD (LVEF <45%) followed for 41±27 months. ICD programming (detection and therapies) was standardized. NSVT was defined as any VT of ≥5 beats which did not met the detection criteria occurring within the first 6 months after ICD implant. We analyzed 2201 NSVTs (10+7 beats), which occurred in 250 of the 416 patients (Median=2; IQR=0–7). The mean cycle length (CL) of NSVT was 323±32 ms (adjusted per multiple episodes/patient, generalized estimating equation method (GEEM)).

Results

During the follow-up, 1441 MVT occurred in 183 patients. After showing a significant correlation between burden of NSVT and the occurrence of appropriate therapies due to MVT (C coefficient=0.68; p<0.001), we observed that subjects with >5 NSVT presented an excess of adjusted risk: HR=1.97 (95% CI=1.45–2.72); p<0.001. However, the adjusted mean CL of NSVTs was similar in patients with (322±34) vs. without MVT (324±26 ms); p=0.3.

Among patients who presented NSVTs and MVTs (n=145 subjects), we analyzed the relationship between the adjusted mean CL of the NSVTs (n=1288 episodes) and the CL of the first appropriate therapy due to MVT occurring subsequently. We found a significant and positive correlation between the two (r=0.88; p<0.001); the strongest correlation was observed in subjects with >5 NSVTs (r=0.97, n=52)). The robustness of such correlation was similar in individuals with ischemic (r=0.86; n=91) versus non-ischemic cardiomyopathy (r=0.90; n=54), and in primary (r=0.86; n=75) versus secondary prevention (r=0.90; n=70). The agreement between the CL of first MVT and the adjusted mean CL of NSVT episodes (GEEM) was determined according to the Bland-Altman Method. The difference between the two values was 2±8.3 ms, with only 7.6% (11/145) of patients in whom the difference between the two CL was outside the concordance limits. The agreement was greater, again, in individuals with >5 NSVTs. As shown in the Figure, in more than 95% of patients both values were within the interval of agreement (0.32±4 ms).

Conclusions

1-The burden of NSVTs occurring early after an ICD implant, but not their CL, is associated with a higher incidence of appropriate therapies due to MVT at follow-up.

2-The CL of the NSVTs and that of the first and subsequent MVTs is virtually the same in patients with higher NSVT burden. Therefore, it could be the same tachycardia, but with different duration.

Figure 1

Funding Acknowledgement

Type of funding source: None

P2879Effectiveness of first versus subsequentes ATP attemps: predictors and clinical consequences

Introduction

Antitachycardia pacing (ATP) terminates the majority (but not all) of slow VTs (S-VT) with a cycle length (CL) >320 ms.

Purpose

To analyze the efficacy, safety and predictors of ATP, comparing the first (ATP-1) to the second (ATP-2) and third (ATP-3) attempts.

Methods

We studied 556 S-VT (CL=354±18 ms; range: 321–415 ms; 1.6% syncopes) occurring in 67 patients. ATP programming was standardized, including three consecutive bursts of 15 pulses at 91% of VT CL.

Results

ATP effectiveness declined significantly from ATP-1 (436/556: 78%) compared to ATP-2 (24/103: 23%) and ATP-3 (10/79: 13%), p<0.01 for all comparisons. The percentage of variation of RR intervals (P-RR, %) was significantly higher prior to effective ATP-1 (2.73±1.45 vs 1.23±0.9; p<0.001). After an ineffective ATP-1, the P-RR decreased dramatically, with no differences between episodes terminated or not at ATP-2 (0.6±0.14 vs 0.44±0.16; p=0.6) or ATP-3 (0.54±0.15 vs. 0.52±0.14; p=0.7). The postpacing interval – CL difference (PPI-CLd) after an unsuccessful ATP-1 was shorter in episodes terminating at ATP-2 or ATP-3 (180±24 vs 211±15 ms; p<0.001) being 200 ms the cut-off point with the best sensitivity and specificity for non-effective ATP-2 and ATP-3 (93% and 74%, respectively). By multivariate analysis, the duration of native QRS complex (dQRS) (ms) was found the only independent predictor of a PPI-CLd ≥200 ms (OR=1.04; p=0.003). The best cutoff point of dQRS for PP-CLd ≥200 ms was 120 ms (sensitivity and specificity of 66% and 79%, respectively).

Several predictors of ATP efficacy were found by logistic regression: a) ATP-1: P-RR (OR=7.3; p<0.001), beta-blockers (OR=4.1; p<0.001) and dQRS (OR=0.95; p<0.001); b) ATP-2: PPI-CLd (OR=0.94; p=0.001) and dQRS (OR=0.96; p=0.04); c) ATP-3: PPI-CLd (OR=0.93; p=0.009).

Patients with a dQRS≥120 ms had a lower adjusted effectiveness of ATP and a higher proportion of S-VT causing syncope. Table.

Table 1 Patients with QRS <120 ms Patients with QRS ≥120 ms p value Adjusted effectiveness of ATP-1 89% (82–96) 70% (59–80) 0.008 Adjusted effectiveness of ATP-2 47% (32–63) 23% (11–35) 0.036 Adjusted effectiveness of ATP-3 18% (3–33) 3% (0–6) 0.003 Adjusted incidence of syncope due to S-VT 0.18% (0–0.6) 4.1% (2.1–6.1) 0.025 Values are expressed as mean (95% CI). Generalized Estimating Equations Method.

Conclusions

The efficacy of ATP in terminating S-VT is mainly due to the ATP-1. The regularization of RR intervals after ineffective ATP-1 underlies the lower efficacy of ATP-2 and ATP-3. Since the dQRS correlated significantly with the PPI-CLd, patients with a dQRS≥120 ms had a lower ATP-1, ATP-2 and ATP-3 effectiveness, leading to a higher incidence of syncope.

P2874Predictors of Electrical Strom among ICD patients: the importance of the burden of non-sustained VTs

Background

Among ICD patients, the burden of non-sustained ventricular tachycardias (NSVT) occurring during the first 6 months after implant is associated independently with an increase in cardiac death. It is unknown whether there are differences between the incidence of Electrical Storm (ES) and the cause of cardiac mortality (CM) according to the burden of NSVT.

Purpose

To determine the relationship between the burden of NSVT occurring early after ICD implant and the risk of ES in the long-term among ICD patients with left ventricular dysfunction.

Methods

In this prospective study, 416 patients (age: 65±11; LVEF: 30±8; ischemic etiology: 62%, primary prevention: 63%) with LVEF <45% and ICD without cardiac resynchronization therapy were followed-up for 41±27 after implant. ICD programming was standardized. NSVT was defined as any ventricular tachyarrhythmia with >5 beats at ≥150 bpm terminating spontaneously before therapy that occurred within the first six months after ICD implant.

Results

A total of 31 patients (7.5%) presenting with ES during the follow-up. After classifying the subjects into three groups according to the burden of NSVT (tertiles): no NSVT (N=166, group 1); 1–5 NSVT (n=130, group 2) and >5 NSVT (n=120, group 3), the cumulative incidence of ES was higher in group 3: 2.4% vs. 3.1% vs. 19.2%, with an average of time from implant to ES significantly shorter (mean [95% CI, months]): 97 (94–100) vs. 103 (99–106) vs. 86 (79–93); p<0.001 for groups 1–2 vs. 3 (log-rank test). Figure. All ESs were due to monomorphic VT in individuals with ≤5 NSVT; however, 19% of ESs were caused by polymorphic VT or VF among patients with >5 NSVT (p<0.05). By multivariate analysis (Cox-regression), LVEF, % (HR=1.06; p=0.026) and >5 TVNS (HR=4.66; p=0.001) were identified as independent predictors of ES. Cardiac mortality (CM) was independently higher in subjects with >5 NSVT (HR=1.7; p=0.03). The most frequent cause of CM was cardiac failure irrespective of NSVT burden (93% in patients with ≤5 NSVT and 79% in >5 NSVT); however CM due to ES was exclusive of individuals with >5 NSVT: 15% vs. 0% (p<0.05).

Figure 1

Conclusions

1. The burden of NSVT occurring during the first 6 months after an ICD implant is associated independently with a higher risk of ES in the long-term. 2. The adjusted risk of ES is 4-fold higher in individuals with >5 NSVT. 3. The most frequent etiology of CM is heart failure; CM due to ES is exclusive of patients with >5 NSVT causing the 15% of deaths in such population.