Juan José de la Vieja

Silent ischaemic brain lesions related to atrial high rate episodes in patients with cardiac implantable electronic devices

AIMS Monitoring capabilities of cardiac implantable electronic devices have revealed that a large proportion of patients present silent atrial fibrillation (AF) detected as atrial high rate episodes (AHREs). Atrial high rate episodes >5 min have been linked to increased risk of clinical stroke, but a high proportion of ischaemic brain lesions (IBLs) could be subclinical. METHODS AND RESULTS We prospectively analysed the incidence of AHRE > 5 min in 109 patients (56% men, aged 74 ± 9 years) and the presence of silent IBL on computed tomography (CT) scan. Mean CHADS2 and CHA2DS2VASc scores were 2.3 ± 1.3 and 3.9 ± 1.6, respectively. Seventy-five patients (69%) had no history of AF or stroke/transient ischaemic attack (TIA). After 12 months, 28 patients (25.7%) showed at least one AHRE. Patients with AHREs were more likely to have history of AF. Computed tomography scan showed silent IBL in 28 (25.7%). The presence of IBL was significantly related to older patients, prior history of AF or stroke/TIA, higher CHADS2 or CHA2DS2VASc scores, and the presence of AHRE. Multivariable analysis demonstrated that AHRE was an independent predictor for silent IBL in overall population [hazard ratio (HR) 3.05 (1.06-8.81; P < 0.05)] but also in patients without prior history of AF or stroke/TIA [HR 9.76 (1.76-54.07; P < 0.05)]. CONCLUSION Cardiac implantable electronic devices can accurately detect AF as AHRE. Atrial high rate episodes were associated to a higher incidence of silent IBL on CT scan. Atrial high rate episodes represent a kind of silent AF where management recommendations are lacking despite the fact that a higher embolic risk is present.

Silent brain infarcts in high blood pressure patients with cardiac implantable electronic devices: unmasking silent atrial fibrillation.

Background: Hypertensive patients present a higher risk for developing atrial fibrillation and its complications. Cardiac implantable electronic devices (CIEDs) have shown reliable atrial fibrillation detection as atrial high-rate episodes (AHREs). The presence of AHRE more than 5 min has been related to increased risk of stroke, but a high proportion of ischemic brain lesions (IBLs) could be subclinical and thromboembolic risk underestimated. Methods: We included hypertensive patients with CIED and we analyzed the incidence of AHRE and the presence of IBL on computed tomography (CT) scan. Results: One hundred and twenty-three patients (57% men) aged 77 ± 8 years were evaluated during a mean follow-up of 15 ± 9 months. AHREs were documented in 46 patients (37%). Cranial CT scan showed silent IBL in 34 patients (27%). Univariate analysis showed that age, CHADS2 and CHADS2VA2Sc scores, history of prior stroke/ transient ischemic attack and the presence of AHRE were significantly related to higher risk for IBL on CT scan (P < 0.05). Multivariate analysis showed that the presence of AHRE more than 5 min [odds ratio 3.05 (1.19–7.81; P < 0.05)] was an independent predictor of IBL. Conclusion: Silent atrial fibrillation detected by CIED as AHRE is really prevalent in hypertensive patients. AHREs were independently associated with a higher incidence of silent IBL on CT scan.

Limitations of the AutoCapture™ Pacing System in patients with cardiac stimulation devices

AIMS AutoCapture (St Jude Medical) is a technological development that confirms ventricular capture analysing the evoked response after a pacing impulse and adjusts the energy output to changes in the stimulation threshold. Although this algorithm is aimed to assure capture minimizing energy consumption, some patients might not benefit from it. The objective of this study is to identify them. METHODS AND RESULTS Long-term AutoCapture efficiency was assessed using the data recorded in the programmer reports of patients undergoing scheduled pacemaker check-ups during 2012 in our institution. We have evaluated 160 consecutive patients (58% men) aged 78 ± 9 years. Pacemaker stimulation mode was DDD in 116 patients (72.5%) and VVI in 44 patients (27.5%). During the scheduled visits for pacemaker check-up, 73 patients (45.6%) showed abnormalities in the long-term AutoCapture function report (high variability in the AutoCapture stimulation threshold and/or out-of-range values). After multivariate analysis, abnormal AutoCapture pattern was associated to the presence of atrial fibrillation [odds ratio (OR) 3.96 (1.59-9.82; P < 0.05)]; and a ventricular pacing ≤25% of the time [OR 4.80 (2.09-11.05; P < 0.05)]. AutoCapture abnormalities were also described in three (1.8%) patients with very low stimulation threshold. CONCLUSION Although AutoCapture algorithm has shown both efficacy and safety, our findings suggest that some patients with atrial fibrillation or those requiring ventricular pacing ≤25% of the time may not benefit from it. Activation of the algorithm should be individualized according to the patients characteristics and long-term AutoCapture pattern checked in the routine follow-up.

CorVue algorithm efficacy to predict heart failure in real life: Unnecessary and potentially misleading information?

Heart failure (HF) hospitalizations have a negative impact on quality of life and imply important costs. Intrathoracic impedance (ITI) variations detected by cardiac devices have been hypothesized to predict HF hospitalizations. Although Optivol™ algorithm (Medtronic, Minneapolis, MN, USA) has been widely studied, CorVue™ algorithms (St. Jude Medical, St. Paul, MN, USA) long‐term efficacy has not been systematically evaluated in a “real‐life” cohort.

How to recognize silent atrial fibrillation in pacemakers and defibrillators—the value of atrial electrograms

Todays pacemakers and defibrillators include diagnostic tools for detecting and treating cardiac arrhythmias like silent atrial fibrillation as atrial high rate episodes (AHREs). This diagnostic capability is crucial to prevent the potential embolic complications this AHREs are related to. However, sometimes data retrieved from diagnostic counters may be misleading reflecting limitations of detection algorithms, which must follow mathematical rules to classify events on a beat-to-beat basis. The incorporation of stored electrograms has been an important milestone in improving the diagnostic capabilities of these devices confirming the arrhythmia diagnosis.

Inappropriate automatic mode switching episodes: What's the mechanism?

We present a case series of five patients reporting abnormal automatic mode switching (AMS) episodes during routinary cardiac defibrillator (ICD) and pacemaker (PM) follow-up. This non-previously described phenomenon was reported to St. Jude Medical (Abbott) Technical Support that confirmed the inappropriate automatic mode switching.

Silent atrial fibrillation in pacemaker early post-implantation period: an unintentionally provoked situation?

Aims Atrial high-rate episodes (AHREs) compatible with silent AF detected in pacemakers (PM) are related to an increased risk of stroke and silent ischaemic brain lesions (IBL) on CT scan. AHREs soon after PM implantation could be related with the procedure itself and the prognosis might be different. Methods and results We analysed the incidence of AHREs >5 min and the presence of silent IBL in 110 patients (56% men, aged 75 ± 9 year-old) with PM and no history of AF, in relation to time from implantation (≤3 months vs. >3 months) and the atrial lead fixation (LF) (active vs. passive). Mean CHADS2 and CHA2DS2VASc scores were 1.9 ± 1.2 and 3.5 ± 1.5, respectively. Time from implantation was ≤3 months in 88 patients (80%). Active LF was used in 55 patients (50%). After 24 ± 9 months, AHREs were present in 40 patients (36.4%). CT-scan showed silent IBL in 26 patients (23.6%). The presence of AHREs at 3 months was more frequent in the patients with recent PM implantation (17% vs. 4.5%, P = 0.09) and significantly related to active LF (OR 5.36, 1.43-20.07; P < 0.05). The presence of silent IBL was related to the detection of AHREs during follow up (OR 3.12, 1.29-7.97; P < 0.05) but not with AHREs at first 3 months (OR 1.58, 0.49-5.05; P = 0.44). Conclusions AHREs occur frequently during the first 3 months after PM implantation and could be related with procedure itself and the use of active LF. AHREs in this period might not be related to worse outcomes and should be interpreted cautiously.

Things are not always what they seem: pacemaker dysfunction or just a technical limitation?

A routinary electrocardiogram (ECG) performed in a 90-year-old patient with sinus node disease and a dual-chamber pacemaker (Endurity MRI, St. Jude Medical) programmed in DDDR mode showed atrial fibrillation (AF) with abnormal stimulation spikes: atrial pacing (AP) despite the presence of AF and ventricular pacing with too short R-R wave intervals or even on the T wave. What are we dealing with? The ECG shows three typical phenomena related to atrial undersensing during AF: atrial pacing (AP) over undetected atrial high-rate activity and ventricular pacing (VP) over the programmed high-rate limit due to ventricular undersensing during post-atrial pacing ventricular blanking interval (PAP VBi) and ventricular safety pacing interval (VSPi). ‘A’ shows AP, despite the presence of AF. We can appreciate

ATRIAL HIGH RATE EPISODES AND SILENT ISCHEMIC BRAIN LESIONS IN PATIENTS WITH CARDIAC IMPLANTABLE ELECTRONIC DEVICES: UNMASKING SILENT ATRIAL FIBRILLATION EMBOLIC RISK

Cardiac implantable electronic devices (CIED) reveal that many patients present silent atrial fibrillation (AF) detected as atrial high rate episodes (AHRE). AHRE >5min have been linked to increased risk of clinical stroke, but a high proportion of ischemic brain lesions (IBL) could be subclinical

Novel electrocardiographic findings related to new cardiac electronic devices functions

An 81-year-old man was evaluated in the out-patient clinic after pacemaker generator replacement with an ECG performed in that moment that was described as “loss of capture in the stimulated beats” and “abnormal number of stimulation spikes” (Fig. 1). The patient was then referred to the ER for pacemaker interrogationwith the suspected diagnosis of pacemaker dysfunction. Seven years ago, the patient had received a dual-chamber pacemaker DDDR because of symptomatic sinus node dysfunction associated to first degree AV-block, left anterior hemiblock and right bundle brunch block. The patient underwent routinary pacemaker controls every year showing normal parameters but an increased right ventricle stimulation threshold (around 3 V at 0.50 ms). It was stable during the last 3 years, without changes in detection values or impedance. When the battery showed ERI (Elective Replacement Indicator), a new generator was implanted (St. Jude Accent ® DR, Minneapolis, USA). This pacemaker is equipped with the AutoCaptureTM Pacing System Technology. Many useful technological improvements have occurred since the first pacemaker implantation in 1958. This ECG illustrates howone of the most used automatic algorithms of the new generation pacemakers, the AutoCaptureTM, works. The AutoCaptureTM Pacing System is an algorithm designed to confirm a response (capture) to each of the pacemaker stimulations and to automatically adjust the energy output of the primary pacing pulse in response to changes in the threshold. This principle is based on the pacemakers ability to recognize the evoked response (the signal resulting from the electrical activation of the myocardium by a pacemaker stimulus) without beingmisled by residual polarization at the electrode–tissue interface [1]. This system monitors every beat for the presence of an evoked response signal and assures capture. After loss of capture, the device automatically searches the thresholds on a regular basis to determine the output energy level requirement. For this operation the AV interval is shortened to a programmable duration (usually 40–50 ms) during the test to avoid fusion with conducted beats. Loss of capture recovery triggers an automatic backup safety pulse to ensure capture in the absence of an evoked response. Automatic output regulation sets the output just above themeasured threshold (0.25 V over the threshold), ensuring the lowest energy level required for capture and thus optimizing device longevity (Fig. 2). The AutocaptureTM algorithm not only decreases energy consumption by keeping the stimulation output slightly above the actual threshold, but also increases patient safety by access to highoutput back-up pulses if there is loss of capture. It offers to the physicians an improved patient safety, a follow-up efficiency and longer device longevity by confirming beat-by-beat capture of each pacemaker stimulation [2].