Bharat K. Kantharia

Novel uses of intracardiac echocardiography with a phased-array imaging catheter

A newer phased-array ultrasound imaging catheter (AcuNav, Siemens, Moutainview, Calif) provides comprehensive anatomic and physiologic data during cardiac interventions. The role of this catheter in percutaneous closure procedures, transseptal ablative procedures, and valvular interventions has been reported. We describe an expanded role of intracardiac echocardiography using AcuNav imaging catheter (Siemens) in 2 clinical situations.

Role of insertable cardiac monitors in anticoagulation therapy in patients with atrial fibrillation at high risk of bleeding

AIMSnWe aimed to ascertain whether an insertable cardiac monitor (ICM)-guided rhythm-control strategy and assessment of atrial fibrillation (AF) burden may allow safe withdrawal and obviate long-term use of oral anticoagulants (OACs) in AF patients at high bleeding risk.nnnMETHODS AND RESULTSnWe implanted ICMs in 70 patients with AF with high risk of stroke (CHADS2 ≥2, CHA2DS2-VASc score ≥2) and bleeding (HAS-BLED score ≥3) after restoration of normal sinus rhythm (NSR) for continuous rhythm monitoring and optimization of antiarrhythmic drugs (AADs) when necessary. Patients were categorized into: (i) Group A (NSR/low AF burden, <1%), (ii) Group B (moderate/variable AF burden), and (iii) Group C (high AF burden, always AF). At patients insistence, OACs were discontinued after proper counselling only if they maintained NSR/low AF burden for ≥3 consecutive months. All patients (age 73.3 ± 11.7 years; 53% male) were followed clinically and with ICM monitoring for 23.5 ± 10.5 months for outcomes including stroke, bleeding, death, device malfunction or infection, and AADs adverse effects. Patients in Group A (n = 43), Group B (n = 20), and Group C (n = 7) had similar CHADS2 (2.09 ± 0.65, 2.05 ± 0.51, and 2.14 ± 0.38, respectively), CHA2DS2-VASc (3.05 ± 1.05, 2.85 ± 0.99, and 2.42 ± 0.53, respectively), and HAS-BLED (3.02 ± 1.01, 3.40 ± 0.68, and 3.00 ± 0.58, respectively) scores (P > 0.05). In 53 (76%) patients (Group A = 41 and Group B = 12) who maintained NSR/low AF burden, OACs were discontinued without adverse events. Severe bleeding occurred in 4 of 17 (24%) patients who remained on OACs.nnnCONCLUSIONnIn AF patients with high bleeding risk, ICM-guided rhythm control with AADs and assessment of AF burden may allow safe discontinuation of OACs.

Diffuse Cerebral Air Embolism Treated With Hyperbaric Oxygen: A Case Report

A 54‐year‐old woman presented for cardiac evaluation of atypical chest pain. Workup included coronary angiography and a left ventriculogram, during which air was inadvertently injected, resulting in the development of an acute right hemisphere syndrome. Right carotid angiography was immediately performed, yielding only a delayed diffuse venous phase without focal vessel cutoffs. Within 60 minutes, the patient underwent hyperbaric oxygen therapy for the suspected cerebral air emboli. After removal from the chamber for technical reasons, she had a generalized tonic‐clonic seizure, and further hyperbaric oxygen therapy was withheld. Initial computed tomography imaging obtained approximately 8 hours after symptom onset showed signs of early right hemispheric edema. Subsequent magnetic resonance imaging studies were markedly abnormal and suggestive of diffuse bilateral but predominantly right‐sided parietal lobe edema with mildly positive diffusion‐weighted imaging. Follow‐up magnetic resonance imaging at 6 months was normal, and the patients neurological examination returned to normal.

Can we predict, prevent, and minimize defibrillator shocks? Lessons learned from “remote monitoring”

s I o f 9 f Beyond their principal role of successfully detecting and treating ventricular tachycardia (VT) and ventricular fibrillation (VF) with overdrive antitachycardia pacing and defibrillation shocks, modern implantable cardioverter-defibrillators (ICDs) are capable of providing sophisticated pacing and resynchronization therapy. They store enormous amounts of technical and patient-related data, such as arrhythmia burden and heart failure status. Device manufacturers recently introduced “remote monitoring” technology, which allows home transmitters to interrogate devices and to download and transmit collected and stored data via the Internet to a protected network. Remote monitoring not only has rapidly shifted the paradigm in device follow-up but has heightened interest in exploring the wealth of available information to better understand device functionality and disease substrates. Irrespective of the indications for ICD placement, given the associated risk factors and comorbidities, the majority of recipients also would be prone, if they have not already experienced, to develop atrial fibrillation (AF). The presence of AF, with its 5% to 30% incidence in the ICD population, is not merely a “nuisance” because it has many detrimental effects. Paroxysmal, persistent, and permanent AF have hazard ratios (HRs) (95% confidence interval] of 1.3 (0.7–2.5), 1.2 (0.6–2.2), and 1.7 (1.0–2.7), respectively, for mortality and 1.2 (0.6–2.2), 1.1 (0.5–2.4), and 2.4 (1.5–4.0), respectively, for appropriate ICD shocks. A ewly detected AF within the first 3 months of ICD placeent carries a significant risk for death with HR of 2.86 1.02–8.05). In patients with left ventricular dysfunction, persistent AF has been shown to cause appropriate ICD shocks and deterioration of heart failure. Furthermore, AF ay be proarrhythmic. In the Jewel AF trial, 8.6% of all T/VF episodes were found to have AF as a preceding or oncomitant rhythm. Interestingly, for consecutive episodes of VT/VF, time to next episode of VT/VF was longer when AF terminated than when it persisted.

Role of cardiovascular implantable electronic devices in delivering individualized disease-guided management of patients with non-valvular atrial fibrillation and high bleeding risk

Abstract Background: Many patients with non-valvular atrial fibrillation (NVAF) with high risk for thromboembolic stroke and bleeding may not wish to continue long-term oral anticoagulants (OACs) to avoid bleeding complications. We aimed to investigate whether AF burden assessment by cardiovascular implantable electronic devices (CIEDs) would allow an individualised disease-guided approach for safe withdrawal of long-term OAC in high-risk patients. Methods and results: We studied 145 patients (age 77.6u2009±u200910.6 years; 49.7% females) with NVAF, CHA2DS2-VASc score ≥2, HAS-BLED score ≥3, in whom CIEDs were implanted. These patients wished to stay off long-term OAC based on their previous adverse bleeding event/s or due to similar events witnessed in the family or friend circle. These patients were grouped into ‘low AF burden’ [nu2009=u2009121 (83%)], or ‘high AF burden’ [nu2009=u200924 (17%)] defined asu2009<24u2009hours or >24u2009hours cumulatively in 30 consecutive days respectively, and followed for 51.2u2009±u200929.8 months. All patients with ‘low AF burden’ were allowed to discontinue OAC, but OAC was resumed in 1 patient who experienced TIA. Bleeding events developed in 9 out of 24 (37.5%) patients with ‘high AF burden’ who were maintained on OAC, as compared to 3 out of 121 (2.47%) patients with ‘low AF burden’ who were off OAC (pu2009<.05). There were 9 (6.2%) deaths unrelated to AF treatment approach. Conclusions: In NVAF patients, AF burden assessment by CIEDs allows an individualised disease-guided approach to safe withdrawal of long-term OAC in patients with high bleeding risk who do not wish to continue long-term anticoagulation.

Entrainment: From a bedside exercise to mathematical formulas

“Entrainment” technique is commonly used during invasive electrophysiology studies and ablation procedures in patients with various cardiac arrhythmias. The principle behind entrainment is resetting of the tachycardia continuously by overdrive pacing at a pacing cycle length (PCL) shorter than the tachycardia cycle length (TCL) such that well-established criteria of “manifest” and “concealed” entrainment are met. While highly useful, entrainment mapping also has few pitfalls and shortcomings. Some arrhythmias simply cannot be entrained because of the absence of prerequisite “excitable gap.” Entrainment is also dictated by dynamic changes in the electrophysiological properties of the circuit. Paced complexes need to overcome refractoriness of the intervening tissue to reach the circuit and excitable gap. The site, rate, and duration of pacing also influence entrainment. For example, since the ventricles are component of orthodromic atrioventricular reciprocating tachycardia, if entrainment is intended from the right ventricle, slower PCL (just slightly faster than TCL) may be adequate because too rapid PCL may terminate tachycardia by retrograde penetration of the atrioventricular node. Likewise, it would be necessary to pace for a longer time from the right ventricle to entrain atrioventricular nodal reentrant tachycardia compared to atrioventricular reciprocating tachycardia. Inference from the postpacing interval (PPI), which is used to determine whether the pacing site is within or outside the circuit, can be prone to error, especially in cases where decremental conduction might occur both within and outside the circuit. Other reasons to erroneous PPI and PPI TCL may be saturation of recordable electrograms by pacing and inaccurate identification of near-field and far-field electrograms. Furthermore, response to ventricular pacing and PPI TCL criteria of supraventricular tachycardia (SVT) differentiation cannot be applied universally. To overcome some of the errors of PPI and PPI TCL and derive more accurate inference, perhaps more emphasis should be given to other parameters such as number of pacing beats needed to entrain (NNE). During entrainment maneuver for intra-atrial reentrant atrial