The effect of cooling rate on the precision of measurement of glow peak 5 in the thermoluminescence of LiF:Mg,Ti (TLD-100).

The effect of natural rapid cooling and oven slow cooling on the precision of thermoluminescence measurements of LiF:Mg,Ti is investigated. Three separate series of measurements resulted in average precisions of 5.1 and 5.0%, respectively. However, the highest precision of 1.7% (1 SD) was achieved for an oven-cooled material.

Device-related complications in subcutaneous versus transvenous ICD: a secondary analysis of the PRAETORIAN trial.

BACKGROUND: The subcutaneous implantable cardioverter-defibrillator (S-ICD) is developed to overcome lead-related complications and systemic infections, inherent to transvenous ICD (TV-ICD) therapy. The PRAETORIAN trial demonstrated that the S-ICD is non-inferior to the TV-ICD with regard to the combined primary endpoint of inappropriate shocks and complications. This prespecified secondary analysis evaluates all complications in the PRAETORIAN trial. METHODS AND RESULTS: The PRAETORIAN trial is an international, multicentre, randomized trial in which 849 patients with an indication for ICD therapy were randomized to receive an S- ICD (N = 426) or TV-ICD (N = 423) and followed for a median of 49 months. Endpoints were device-related complications, lead-related complications, systemic infections, and the need for invasive interventions. Thirty-six device-related complications occurred in 31 patients in the S-ICD group of which bleedings were the most frequent. In the TV-ICD group, 49 complications occurred in 44 patients of which lead dysfunction was most frequent (HR: 0.69; P = 0.11). In both groups, half of all complications were within 30 days after implantation. Lead-related complications and systemic infections occurred significantly less in the S-ICD group compared with the TV-ICD group (P < 0.001, P = 0.03, respectively). Significantly more complications required invasive interventions in the TV-ICD group compared with the S-ICD group (8.3% vs. 4.3%, HR: 0.59; P = 0.047). CONCLUSION: This secondary analysis shows that lead-related complications and systemic infections are more prevalent in the TV-ICD group compared with the S-ICD group. In addition, complications in the TV-ICD group were more severe as they required significantly more invasive interventions. This data contributes to shared decision-making in clinical practice.

Efficacy and Safety of Appropriate Shocks and Antitachycardia Pacing in Transvenous and Subcutaneous Implantable Defibrillators: Analysis of All Appropriate Therapy in the PRAETORIAN Trial.

BACKGROUND: The PRAETORIAN trial (A Prospective, Randomized Comparison of Subcutaneous and Transvenous Implantable Cardioverter Defibrillator Therapy) showed noninferiority of subcutaneous implantable cardioverter defibrillator (S-ICD) compared with transvenous implantable cardioverter defibrillator (TV-ICD) with regard to inappropriate shocks and complications. In contrast to TV-ICD, S-ICD cannot provide antitachycardia pacing for monomorphic ventricular tachycardia. This prespecified secondary analysis evaluates appropriate therapy and whether antitachycardia pacing reduces the number of appropriate shocks. METHODS: The PRAETORIAN trial was an international, investigator-initiated randomized trial that included patients with an indication for implantable cardioverter defibrillator (ICD) therapy. Patients with previous ventricular tachycardia <170 bpm or refractory recurrent monomorphic ventricular tachycardia were excluded. In 39 centers, 849 patients were randomized to receive an S-ICD (n=426) or TV-ICD (n=423) and were followed for a median of 49.1 months. ICD programming was mandated by protocol. Appropriate ICD therapy was defined as therapy for ventricular arrhythmias. Arrhythmias were classified as discrete episodes and storm episodes (≥3 episodes within 24 hours). Analyses were performed in the modified intention-to-treat population. RESULTS: In the S-ICD group, 86 of 426 patients received appropriate therapy, versus 78 of 423 patients in the TV-ICD group, during a median follow-up of 52 months (48-month Kaplan-Meier estimates 19.4% and 17.5%; P=0.45). In the S-ICD group, 83 patients received at least 1 shock, versus 57 patients in the TV-ICD group (48-month Kaplan-Meier estimates 19.2% and 11.5%; P=0.02). Patients in the S-ICD group had a total of 254 shocks, compared with 228 shocks in the TV-ICD group (P=0.68). First shock efficacy was 93.8% in the S-ICD group and 91.6% in the TV-ICD group (P=0.40). The first antitachycardia pacing attempt successfully terminated 46% of all monomorphic ventricular tachycardias, but accelerated the arrhythmia in 9.4%. Ten patients with S-ICD experienced 13 electrical storms, versus 18 patients with TV-ICD with 19 electrical storms. Patients with appropriate therapy had an almost 2-fold increased relative risk of electrical storms in the TV-ICD group compared with the S-ICD group (P=0.05). CONCLUSIONS: In this trial, no difference was observed in shock efficacy of S-ICD compared with TV-ICD. Although patients in the S-ICD group were more likely to receive an ICD shock, the total number of appropriate shocks was not different between the 2 groups. Registration: URL: https://www.clinicaltrials.gov; Unique identifier: NCT01296022.

Investigation of the Utility of the Audible Alert in Recent Generation Medtronic Implantable Cardioverter Defibrillators.

BACKGROUND: Medtronic implantable cardioverter defibrillators (ICDs; Medtronic Inc., Mounds View, MN, USA) are equipped with Patient Alert™, a feature in which the ICD generator emits a series of audible tones to notify patients of possible system malfunction. A prior study of this issue revealed that only 50% of patients with older Medtronic devices were able to hear alerts. More recently, Medtronic has incorporated modifications to the alert. Therefore, we studied how frequently alert tones emitted by the current generation of Medtronic ICDs are audible by patients. METHODS: A series of patients were evaluated in an outpatient ICD clinic. Alert tones were demonstrated using a device programmer in a quiet room and in the presence of low-level background noise. Patients reported whether they heard the tones, and they completed questionnaires regarding the tones. RESULTS: The total sample size was 100 patients, 81 male, who ranged from 29 years to 94 years of age (mean age 72.1 ± 11.8). Among the study subjects, 46% were older than 75 years, 41% were between 55 years and 75 years, and 13% were younger than 55 years. In the absence of background noise, 94% of patients were able to hear both alerts, 1% heard only one alert, and 5% heard neither. In the presence of background noise, 88% of patients heard both the alerts, 7% heard only one alert, and 5% heard neither alerts. CONCLUSIONS: Our results demonstrate that alert tones in recent generation Medtronic ICDs have improved audibility, compared to prior published data, among a large outpatient ICD population.

Alert tones are frequently inaudible among patients with implantable cardioverter-defibrillators.

BACKGROUND: Current management guidelines for patients with Medtronic Sprint Fidelis ICD leads (Medtronic Inc., Minneapolis, MN, USA) include prominent use of Patient Alert, a feature in which the ICD generator emits audible beeps at two programmable frequencies. Because hearing loss is highly prevalent beyond the sixth decade of life, the utility of this feature is unclear. Therefore, we conducted a survey of patients' ability to hear the Medtronic Patient Alert. METHODS: During visits to an outpatient device clinic, patients with Medtronic ICDs were evaluated for their ability to hear ICD tones. RESULTS: The patient group consisted of 102 patients. Patients older than 70 years comprised 68% of the sample, with 16% between 60 and 70, and 17% younger than 60 years. Of the 102 patients, 59% (56% of males and 70% of females) were able to hear at least one tone. Ability to hear ICD tones decreased with advancing age. Among patients over 60 and 70 years, 52% and 43%, respectively (P < 0.001 vs. patients below 60 and 70 years), could hear at least one tone. CONCLUSIONS: The Patient Alert feature is not useful among a large proportion of ICD patients. Patients with Sprint Fidelis leads should be evaluated for their ability to hear audible ICD tones. For patients who cannot hear the Patient Alert feature, a wireless remote monitoring and/or daily application of a magnet by a caregiver should be considered. Device manufacturers should include nonauditory alert technologies such as wireless remote monitoring and vibratory stimulation in future devices.

Aortic valve vegetation without endocarditis.

We present a 30-year-old man with an acute middle cerebral artery territory infarction. A transesophageal echocardiogram showed a large, highly mobile mass attached to the patient's aortic valve. We discuss the differential diagnosis of a cardiac mass that includes infection, tumor, and thrombus. A complete workup showed no evidence of systemic infection but did reveal the presence of antiphospholipid antibodies. The patient also had a history of a right lower extremity deep venous thrombosis. Anticoagulation therapy was started, and follow-up showed complete resolution of the aortic valve lesion. This case highlights that when a valvular vegetation is encountered in a clinical setting that does not suggest infectious endocarditis, the diagnosis of antiphospholipid antibody syndrome should be considered. This case and our review of the literature suggest that vegetations in antiphospholipid antibody syndrome, no matter how large and ominous in appearance, can be treated successfully with anticoagulation and vigilant observation.

The electrical substrate of vagal atrial fibrillation as assessed by the signal-averaged electrocardiogram of the P wave.

BACKGROUND: The autonomic nervous system is thought to be involved in the initiation of atrial fibrillation (AF). However, there is a distinct entity of vagal AF characterized by episodes occurring at rest, postprandially, or during sleep. The purpose of this study was to compare intraatrial conduction in patients with vagally mediated AF to those with nonvagal AF, using the signal-averaged electrocardiogram (SAECG) of P wave. METHODS: SAECG of P wave was performed in 58 patients with AF using the Marquette Medical System, and the mean filtered P-wave duration (SAPW) was measured. Nine patients were categorized as having pure vagal AF (Group I), and 42 patients as having nonvagal AF (Group II); the remaining seven patients were excluded from analysis because of incomplete data. RESULTS: The patients in Group I were significantly younger and more likely to have paroxysmal lone AF, as compared to those in Group II. There was no significant difference in left atrial size and left ventricular function in the two groups. The mean SAPW was significantly shorter in Group I when compared to Group II (118 +/- 5 ms vs 149 +/- 39 ms, P < 0.001). Whereas all patients in Group I had a normal SAPW, 79% of patients in Group II had an abnormal SAPW (P < 0.001). A normal SAPW was significantly predictive of vagal AF independent of other co-variables. CONCLUSIONS: (1) Patients with vagal AF are younger, and invariably have paroxysmal lone AF. (2) SAPW is normal and significantly shorter in vagal AF when compared to patients with nonvagal AF. (3) This suggests that those in the vagal AF population have normal intraatrial conduction, which has implications for AF ablation in these patients.

Multimodal characterization of a large right atrial mass after surgical repair of an atrial septal defect.

A 43-year-old woman with exertional dyspnea and a history of surgically repaired atrial septal defect was referred for a transthoracic echocardiogram, which demonstrated a large, mobile mass in her right atrium. The mass was further characterized with contrast transesophageal echocardiography (TEE) and delayed enhancement MRI, which together suggested a thrombus, attached to the eustachian valve and prolapsing through the tricuspid valve. The mass was resected and the diagnosis confirmed on histopathologic examination. This case illustrates the utility of a multimodal approach in characterizing cardiac masses.

Elevated homocysteine levels in patients with end-stage renal disease.

PURPOSE: To examine the effect of hemodialysis on plasma homocysteine levels, and the relationship of these values to clinical cardiovascular events in patients with end-stage renal disease (ESRD). METHODS: Adults undergoing chronic hemodialysis were studied at baseline and at six months. Their clinical histories were obtained at the baseline visit, and measurements of plasma homocysteine concentration were made immediately prior to and following routine dialysis. The occurrence of clinical cardiovascular events was assessed over six months. RESULTS: We enrolled 147 patients (85 men and 62 women, age 58 +/- 15 years) who required hemodialysis for 3.4 +/- 3.4 years (mean +/- SD). The median homocysteine level for this population (including both pre- and post-dialysis values) was 17.3 micromoles/L. Mean pre-dialysis plasma homocysteine levels of patients with clinical cardiovascular disease did not differ significantly from those without the disease (22.5 +/- 9.9 vs. 25.4 +/- 24.5 micromoles/L, respectively), nor did post-dialysis levels differ between these populations. During six months follow-up, rates of ischemic events were not related to hyperhomocysteinemia. The difference between mean pre- and post-dialysis homocysteine levels (26.3 +/- 19.7 and 15.6 +/- 11.4 micromoles/L, respectively) and the decline in homocysteine over the course of a single dialysis treatment session (10.3 +/- 10.2 micromoles/L) were highly significant (p<0.0005). CONCLUSIONS: Plasma homocysteine levels were elevated in 82% of 147 patients with ESRD and fell to the normal range in a majority of patients during a single dialysis treatment session. Mean pre-dialysis levels did not change significantly over six months, however, and plasma homocysteine levels did not predict cardiovascular events in this population. There was also a trend towards worse outcomes in patients with lower homocysteine levels, which correlates to findings from recent studies. Further studies are needed to clarify the association between hyperhomocysteinemia and coronary risk in patients with ESRD.

Imaging of high-risk plaque.

'High-risk' or 'vulnerable' plaques in the coronary arteries have characteristics that make them more prone to disruption and subsequent thrombosis -- the mechanisms of most acute coronary syndromes (ACS). There are a number of imaging modalities that are capable of visualizing these features. This article discusses invasive modalities for identifying 'high-risk' plaque such as intravascular ultrasound, coronary angioscopy, optical coherence tomography, near-infrared spectroscopy and coronary thermography. It also discusses the use of noninvasive modalities such as computed tomography MRI and ultrasound. When these imaging modalities are combined with standard cardiac risk factors and more novel markers of systemic inflammation and thrombogenicity we can improve our ability to identify the 'high-risk' patient.