Effective prediction of response to cardiac resynchronization therapy using a novel program of gated myocardial perfusion single photon emission computed tomography.

AIMS: The limitation of QRS duration as a surrogate measure for left ventricular (LV) mechanical dyssynchrony (LVMD) in cardiac resynchronization therapy (CRT) patient selection encourages seeking alternatives to QRS duration. Exploring the potential of an analysis program of electrocardiographically gated myocardial perfusion single photon emission computed tomography (SPECT) (GMPS) for the estimation of LVMD to predict CRT response. METHODS AND RESULTS: Twenty-four patients undergoing CRT for advanced heart failure caused by non-ischaemic cardiomyopathy were studied. Gated myocardial perfusion single photon emission computed tomographies were performed in the setting of temporary CRT suspension after 1 week of CRT adoption. The GMPS data were computed with a novel program capable of segmental LV time-volume analysis. When a brain natriuretic peptide (BNP) value decreased >50% at 6-month follow-up, the patient was defined as a CRT responder. Receiver operating characteristic (ROC) curves for identification of responders were analysed for standard deviation of time to end systole (TES-SD) among 17 LV segments. Linear regression analyses demonstrated that an increase in percentage reduction in BNP level at 6-month follow-up was predicted by an increase in TES-SD (R(2) = 0.21, P = 0.023). The TES-SD in responders (n = 15, 62.5%) was higher than that in non-responders (100 ± 51 vs. 41 ± 17 ms, P = 0.0008). A cutoff value of TES-SD >49 ms predicted responders with 100% sensitivity and 78.8% specificity and the area under the ROC curve was 0.881 for TES-SD (P = 0.002). CONCLUSIONS: The estimation of LVMD using this novel GMPS program could be an alternative or a complementary approach to QRS duration in CRT patient selection. This finding warrants further assessment of our approach in larger studies.

The role of echocardiography in predicting responders to cardiac resynchronization therapy.

BACKGROUND: This multicenter prospective cohort study aimed to identify both ability of echocardiographic parameters to detect cardiac resynchronization therapy (CRT) volume responders and relation of these parameters with clinical outcomes. METHODS AND RESULTS: CRT responder was defined as ≥ 15% reduction of left ventricular (LV) end-systolic volume at 6 months. Seven echocardiographic dyssynchrony parameters were evaluated. The clinical endpoint comprised time to death from any cause or unplanned hospitalization for a major cardiovascular event. Of the 217 patients enrolled, 63 percent were classified as volume responders, in whom significantly fewer events occurred than in non-responders (log rank, P < 0.001). No single echocardiographic criterion had significant power to detect volume responders, but a combining measurement of dyssynchrony between septum and LV free wall with M-mode and tissue Doppler imaging was independently associated with volume responders. In addition, this combined parameter was associated with the endpoint (hazard ratio, 0.66, 95% confidence interval 0.30-0.98, P = 0.04). In contrast, left bundle branch block was identified as an independent predictor of volume responders and more strongly associated with the endpoint (hazard ratio, 0.38, 95% confidence interval 0.20-0.72, P = 0.003). CONCLUSIONS: Echocardiographic parameters did not show significant power to detect CRT responders independently.

Difference in percentage of ventricular pacing between two algorithms for minimizing ventricular pacing: results of the IDEAL RVP (Identify the Best Algorithm for Reducing Unnecessary Right Ventricular Pacing) study.

AIMS: Managed ventricular pacing (MVP) and Search AV+ are representative dual-chamber pacing algorithms for minimizing ventricular pacing (VP). This randomized, crossover study aimed to examine the difference in ability to reduce percentage of VP (%VP) between these two algorithms. METHODS AND RESULTS: Symptomatic bradyarrhythmia patients implanted with a pacemaker equipped with both algorithms (Adapta DR, Medtronic) were enrolled. The %VPs of the patients during two periods were compared: 1 month operation of either one of the two algorithms for each period. All patients were categorized into subgroups according to the atrioventricular block (AVB) status at baseline: no AVB (nAVB), first-degree AVB (1AVB), second-degree AVB (2AVB), episodic third-degree AVB (e3AVB), and persistent third-degree AVB (p3AVB). Data were available from 127 patients for the analysis. For all patient subgroups, except for p3AVB category, the median %VPs were lower during the MVP operation than those during the Search AV+ (nAVB: 0.2 vs. 0.8%, P < 0.0001; 1AVB: 2.3 vs. 27.4%, P = 0.001; 2AVB: 16.4% vs. 91.9%, P = 0.0052; e3AVB: 37.7% vs. 92.7%, P = 0.0003). CONCLUSION: Managed ventricular pacing algorithm, when compared with Search AV+, offers further %VP reduction in patients implanted with a dual-chamber pacemaker, except for patients diagnosed with persistent loss of atrioventricular conduction.

Quantitative assessment of dyssynchrony using ECG-gated SPECT myocardial perfusion imaging prior to and following cardiac resynchronization therapy.

Cardiac resynchronization therapy (CRT) assists patients with advanced heart failure (HF) by improving left ventricular (LV) dyssynchrony, but there are significant numbers of non-responders, 1 reason being that the QRS duration is used as the only surrogate determinant of mechanical dyssynchrony, so an effective indicator of LV dyssynchrony is required. The present patient, who had HF, underwent CRT and showed clinical improvement with marked LV reverse remodeling. The regional contraction timing in the LV was assessed with software developed in an application on ECG-gated SPECT myocardial perfusion imaging that depicts the time-volume relationship of the segmented ventricular myocardium and the dispersion of time to end-systole as an expression of dyssynchrony. It was reduced in this patient following CRT. Discordance of systole in regional myocardial segments may present as mechanical dyssynchrony in the LV and could be used as an alternative to QRS duration. Quantitative assessment of dyssynchrony may be possible using this novel method, but further evaluation of the methodology is required.

Noninvasive risk stratification of subjects with a Brugada-type electrocardiogram and no history of cardiac arrest.

BACKGROUND: Recent studies suggest that the Brugada-type electrocardiogram (ECG) is much more prevalent than the manifest Brugada syndrome. Although invasive electrophysiologic investigations have been proposed as a risk stratifier, their value is controversial, and alternative noninvasive techniques may be preferred. We sought a noninvasive strategy to detect a high-risk group in a long-term follow-up study of subjects with a Brugada-type ECG, and no history of cardiac arrest. METHODS: This study enrolled 124 consecutive subjects with a Brugada-type ECG. Prognostic indices included: age, sex, a family history of sudden death, syncopal episodes, a spontaneous coved-type ST-segment elevation, maximal magnitude of ST-segment elevation, a spontaneous change in ST segment, a mean QRS duration, maximal QT interval, QT dispersion, late potentials (LP) by signal-averaged ECG, and microvolt T-wave alternans. RESULTS: Of the 124 subjects, 20 consenting subjects had an implantable defibrillator before follow-up. During a 40 +/- 19-month follow-up, 12 subjects (9.7%) reached one of the endpoints (sudden death or ventricular tachyarrhythmia). Of the 12 risk indices, a family history of sudden death, syncopal episodes, a spontaneous coved-type ST-segment elevation, a spontaneous change in ST segment, and LP had significant values. In multivariate analysis, a spontaneous change in ST segment had the most significance (a relative hazard, 9.2; P = 0.036). Combined assessment of this index and other significant indices obtained higher positive predictive values (43-71%). CONCLUSIONS: A spontaneous change in ST segment is associated with the highest risk for subsequent events in subjects with a Brugada-type ECG. The presence of syncopal episodes, a history of familial sudden death, and/or LP may increase its value.

Relationship between ST-segment morphology and conduction disturbances detected by signal-averaged electrocardiography in Brugada syndrome.

BACKGROUND: Although arrhythmogenesis of Brugada syndrome is still unknown, it has been reported to be associated with conduction disturbances. Two ST-segment morphologies (coved and saddle-back patterns) have been described in this syndrome. No study has sought to determine which morphology has stronger conduction disturbances, thereby associating with life-threatening events. METHODS: Forty-six patients who presented the Brugada-type ECG with either of a characteristic coved (n = 25) or saddle-back (n = 21) pattern of ST-segment morphology underwent signal-averaged ECG (SAECG). SAECG parameters, and the history of life-threatening events defined as syncope or aborted sudden death, were compared between groups. RESULTS: Although filtered QRS duration did not differ between groups, the incidence of late potentials in the coved group was higher than in the saddle-back group (22 patients (88%) versus 4 patients (19%); P < 0.01), showing lower RMS40 and longer LAS40. Life-threatening events occurred in 17 patients (68%) in the coved group and 7 patients (33%) in the saddle-back group (P = 0.02). CONCLUSION: The coved pattern of ST segment was more closely related to conduction disturbances than the saddle-back pattern in patients with Brugada-type ECG. Life-threatening events were more common in patients with the coved ST-segment elevation. Conduction disturbances in the coved pattern of ST segment may reflect a substrate of arrhythmogenesis in Brugada syndrome.

Time course for resolution of left atrial appendage stunning after catheter ablation of chronic atrial flutter.

OBJECTIVES: This study assessed the time course of resolution of left atrial appendage (LAA) stunning after catheter ablation of chronic atrial flutter (AFL). BACKGROUND: Although the presence of LAA stunning after ablation of chronic AFL calls for anticoagulation in the post-cardioversion period, limited information has been obtained, particularly regarding its duration. METHODS: Sixteen patients who underwent ablation of chronic, pure AFL were studied, only five of whom had structural heart disease and one of whom had a reduced left ventricular ejection fraction. The LAA emptying velocities (LAAEV) and left atrial spontaneous echo contrast (SEC) were assessed using transesophageal echocardiography before, within 24 h after, one week after, and two weeks after ablation. RESULTS: Within 24 h after ablation, the LAAEV decreased from 39 +/- 10 cm/s during AFL to 21 +/- 10 cm/s during sinus rhythm (p < 0.01), with eight patients (50%) having documented SEC. After one week, the LAAEV increased (39 +/- 17 cm/s, p < 0.01 vs. within 24 h) and SEC resolved in five of eight patients. After two weeks, the increase in LAAEV persisted (54 +/- 14 cm/s, p < 0.01 vs. 1 week) and SEC was no longer present in any of the patients. The numbers of patients with LAAEV >30 cm/s and absence of SEC were three within 24 h, 11 at one week, and 16 at two weeks after ablation. CONCLUSIONS: Patients with chronic, pure AFL and preserved left ventricular function who will undergo catheter ablation may not require anticoagulation therapy for more than two weeks after the procedure because of the presence of forceful mechanical LAA contractions and the absence of SEC.

Evaluation of bi-atrial pacing and single site right atrial pacing for the prevention of atrial fibrillation.

Atrial resynchronization resulting from simultaneous pacing of the atria may adjust inter- or intra-atrial asynchrony and prevent atrial fibrillation (AF). The purpose of this study was to assess the efficacy of bi-atrial pacing (BAP) in preventing AF, and the safety of this system. The effect of BAP was compared with single site right atrial pacing (RAP) in 6 patients with sick sinus syndrome and paroxysmal AF in a prospective switchover trial. P wave duration was significantly reduced during BAP (p<0.01). Pacing threshold, atrial wave amplitude and the lead impedance presented no significant differences at implant, 1 week and 3 months after implantation, respectively (NS). The number of AF episodes significantly decreased during both RAP and BAP compared with the control (p<0.01). Although the number of premature atrial contractions was significantly less during BAP than RAP (p<0.05), there were no significant differences of AF episodes between the two. The percentage of pacing was achieved in only 70% during both pacing modes. BAP was safe and reliable in this follow-up period and can prevent AF. These findings provide encouragement for further study and observation of BAP to prevent AF.