José Antonio Iglesias

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.

An Authoring Tool for Building Adaptive Learning Guidance Systems on the Web

In the field of guided learning on the Internet we present, in this paper, an interactive tool for designing intelligent tutoring systems on the web. Our tool makes easier the creation of an ontology describing the content model for a given course. Such ontology contains information about classes and instances, reflecting the structure and components for the later creation of an adaptive course, using our web-based runtime course manager system. Our authoring tool generates XML code to improve course understanding as well as transportability and processing by our runtime system, which means that the generated code will reflect, in an easier way, the course structure and contents, being readable for most of users and course designers.

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.

Anodal Stimulation in Biventricular Pacing: Unrecognized and Misinterpreted Phenomenon

An 84-year-old patient with history of nonischemic dilated cardiomyopathy with severe systolic dysfunction (left ventricular ejection fraction [LVEF] 30%), heart failure symptoms (New York Heart Association [NYHA] class III), sinus rhythm, and left bundle branch block (LBBB; QRS duration 140 ms) with a cardiac resynchronization therapy (CRT) pacemaker AnthemTM (St. Jude Medical, St. Paul, MN, USA) attended to scheduled device check-up (Fig. 1). Since CRT implantation 1 year before, the patient’s clinical situation had mildly improved to NYHA classes II-III, and LVEF was 35%. Device interrogation showed a biventricular pacing >99%. Right atrial and right ventricular (RV) stimulation threshold tests were performed normally (0.75 V at 0.4 ms and 0.75 V at 0.5 ms, respectively). Automatic left ventricular (LV) stimulation threshold was 3.0 V at 0.5 ms in bipolar configuration (tip LV—proximal ring RV). In order to optimize LV output, stimulation threshold for both configurations (bipolar and unipolar) were assessed using simultaneous electrocardiogram recording. LV stimulation threshold test in unipolar configuration showed a threshold of 2.75 V at 0.5 ms. LV threshold test in bipolar configuration (tip LV—proximal ring RV) showed an interesting phenomenon: at the beginning of the test, LV stimulation produced narrow biventricular stimulation QRS morphology; with the decreasing output energy it changed to RV stimulation QRS morphology and finally it showed lost capture (Fig. 2).

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.

Ineffective appropriate shocks in coronary artery spasm disease: when defibrillation is not enough

A 50-year-old woman without relevant medical history or risk factors received a single-chamber Fortify Assura (St Jude Medical) implantable cardioverter defibrillator (ICD) after recovering from sudden cardiac death (SCD). No structural heart disease was documented and coronary angiogram performed showed normal coronary arteries. Submuscular left-sided ICD implantation with dual-coil electrode was performed without incidences, defibrillation test was not performed. ICD was programmed in VVI 40 bpm for bradycardia and two zones for tachycardia settings (170–200 bpm monitor and > 200 bpm with maximum energy shocks: 36J+40Jx5, RV to SVC&can, biphasic, tilt 65%/65%, 5.6 ms). The patient was discharged and some weeks later was readmitted after syncope. ICD was interrogated showing a ventricular fibrillation (VF) episode that is correctly detected and treated with appropriate ICD shocks. Stored intracardiac electrograms showed ineffective shocks at maximum energy (Fig. 1a). ICD parameters were in the normal limits. Defibrillation test was performed showing successful VF defibrillation at low energy shocks (Fig. 1b). Telemetry ECG monitoring during admission showed a progressive ST elevation coincidental with chest discomfort and palpitations (Fig. 2) compatible with nonpreviously diagnosed coronary artery spasm (CAS). The episode was sustained developing polymorphic ventricular tachycardias and VF which were correctly detected by the ICD (Fig. 3). However, high-energy appropriate shocks applied were ineffective restoring sinus rhythm. In fact, sinus rhythm was restored spontaneously and ST segment normalized some minutes later. The patient started high doses of calcium channel blockers (diltiazem 120 mg/8 h) and remains without recurrences after over 3 years of follow-up. CAS is a more common cause of SCD than previously expected in patients with absence of coronary artery disease [1]. Recurrent episodes and ventricular arrhythmias may be prevented if CAS can be effectively addressed with risk factor modification and ongoing treatment with nitrates and calcium channel blockers. Patients with lifethreatening ventricular tachyarrhythmias secondary to CAS are at particularly high-risk for recurrence. In spite of medical intervention or if compliance is poor, 6% of patients suffered new events in the long-term. ICD implantation could be considered in secondary prevention [2]. Unfortunately, ICD therapies might not be efficient to prevent SCD in the setting of new prolonged ischemic episodes and during the subsequent reperfusion phase. The efficacy of ICD therapy may be hampered throughout refractory severe ischemia [3]. As shown in Fig. 1, successful low-energy shocks during defibrillation test at normal conditions does not imply the same efficacy during ischemic conditions. This fact highlights the importance of aggressive medical therapy directed against CAS in addition to ICD implantation in these patients. In our case, the patient was untreated because she received the ICD before being diagnosed of CAS. Further studies are needed to evaluate the role of ICD in CAS patients under optimal treatment. * Juan Benezet-Mazuecos jbenezet@fjd.es

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.