Causes of Failure to Capture in Pacemakers and Implantable Cardioverter-defibrillators.

The number of patients with implantable electronic cardiac devices is continuously increasing. As more pacemakers and implantable cardioverter-defibrillators (ICDs) are being placed, a basic understanding of some troubleshooting for devices is becoming essential. Loss of capture can be an emergent presentation for an unstable patient and can be encountered intermittently in hospitalized patients. There are many causes for a loss of capture, with the timing of the implant having a high correlation with certain causes over others. The most common acute cause just after the insertion procedure is lead dislodgement or malposition. In comparison, an increase in the required threshold promoting a loss of capture can happen after months to years of insertion of the pacemaker or ICD. This change can be due to a cardiomyopathy, fibrosis medications, metabolic imbalance, lead fracture, or an exit block. Loss of capture can also occur from external electrical stimuli and inappropriate pacemaker or ICD settings. Further, there are also potential noncardiac causes, such as medications, electrolyte imbalance, and acidemia. A knowledge of these factors is essential for health care providers, given the morbidity and mortality that can potentially be associated with device-related issues, especially in patients who are dependent on the included pacing function.

Challenges in Treatment of Inappropriate Sinus Tachycardia.

BACKGROUND: Inappropriate Sinus Tachycardia (IST) is a clinical syndrome characterized by a sinus heart rate inexplicably higher than one hundred beats per minute at rest that is associated with symptoms like palpitations, dyspnea or dizziness in the absence of primary causes of tachycardia. The diagnosis requires exclusion of other causes of tachycardia including medications/substances (such as anti-cholinergic, beta-blocker withdrawal, caffeine, and alcohol) or medical conditions (such as panic attacks, pulmonary embolism, fever, hyperthyroidism, hypovolemia, anemia, and pain). METHODS: Work up should include an EKG to differentiate other causes of tachycardia, 24 hour- Holter monitor if indicated, serum thyroid levels, hemoglobin levels and toxicology screen. Electrophysiological studies are not routinely recommended, but should be considered in certain patients in whom concurrent supraventricular tachycardia is suspected. CONCLUSION: The underlying pathology in IST is yet to be completely understood. However, it is thought that the causes of IST can be broadly classified into two groups; either as an intrinsic increase in sinus node automaticity or an extrinsic cause. Among extrinsic causes, there is evolving evidence that IgG anti-ß receptor antibodies are found in IST causing tachycardia. Managing patients with IST includes lifestyle modification, non-pharmacological and pharmacological interventions. Ivabradine has recently emerged as an effective treatment of IST and was shown to be superior to beta-blockers.

Budd-Chiari syndrome after liver transplantation resulting from inferior vena cava occlusion at the suture line.

A 64-year-old male with Budd-Chiari syndrome (BCS) due to inferior vena cava (IVC) occlusion after liver transplant presented with massive ascites and lower extremity edema. He was found to have chronic total occlusion of the supra-hepatic IVC with thrombosis in the infra-hepatic IVC, hepatic, renal, and iliac veins. Attempts to recanalize the occlusion by multiple operators failed. He was not a surgical candidate. The patient underwent venography of the IVC, and placement of a McNamara catheter for catheter-directed thrombolysis on the first day. The second day, he underwent right internal jugular access with contrast injections to mark the superior aspect of the occlusion via a Multipurpose catheter. An adult transseptal needle (Bard Electrophysiology Division C. R. Bard, Inc., Lowell, MA, USA) was used to create a tract through a 6 French Raabe Sheath and traverse the occlusion. A 10-mm Snare (Cook, Bloomington, IN, USA) cranially retracted the guidewire. Intravascular ultrasound was performed to further delineate the diameter of the IVC at the lesion before dilation with a 6.0 mm × 40 mm PTA balloon and a 10 mm × 29 mm Palmaz Stent (Cordis Corporation, Bridgewater, NJ, USA) deployment. The patient lost 24.6 kg in 2 weeks with resolution of ascites and pedal edema. .

Outcomes after endocarditis or device infection in patients with left ventricular epicardial leads versus coronary sinus leads.

BACKGROUND: There is scant data about outcomes in patients with left ventricular epicardial (LVE) leads who develop endocarditis or device-related infection. OBJECTIVE: This retrospective study evaluated mortality and recurrence of infection among patients with LVE leads in comparison to patients with endovascular coronary sinus (CS) leads after the development of endocarditis or device-related infection. METHODS: Patients with cardiac resynchronization therapy (CRT) devices who developed endocarditis or pocket infection over 5 years at Cleveland Clinic were included in the study. The groups were all patients with LVE leads versus CRT devices without epicardial leads that developed endocarditis or pocket infection. Mortality was assessed using the Social Security Death Index and re-infection was assessed by reviews of the medical record. RESULTS: Prospective extraction of the CRT device and leads occurred among all 50 patients with CS leads and 8 of the 14 patients with LVE leads. The survival rate was 92.9 versus 92 % and freedom from re-infection rate was 64.3 versus 80 % in the patients with LVE leads versus CS leads, respectively, over 1 year (P value = 0.918 and 0.226, respectively). At 3 years, the survival rate in LVE lead group was 92.9 % and freedom from re-infection rate was 64.3 % in comparison to survival rate of 90 % and freedom from re-infection rate of 68 % in the CS group (P value = 0.751 and 0.798, respectively). CONCLUSION: After development of endocarditis or pocket infection, no statistically significant differences were seen in mortality, or recurrent infection between patients with LVE leads and those with CS leads.

Systemic antibody responses to the immunodominant p23 antigen and p23 polymorphisms in children with cryptosporidiosis in Bangladesh.

Cryptosporidium is a major cause of diarrhea in children in developing countries. However, there is no vaccine available and little is known about immune responses to protective antigens. We investigated antibody responses to p23, a putative vaccine candidate, in children in Bangladesh with cryptosporidiosis and diarrhea (cases) and uninfected children with diarrhea (controls), and p23 gene polymorphisms in infecting species. Serum IgM, IgG, and IgA responses to p23 were significantly greater in cases than controls after three weeks of follow-up. Cases with acute diarrhea had significantly greater serum IgA and IgM responses than those with persistent diarrhea, which suggested an association with protection from prolonged disease. The p23 sequences were relatively conserved among infecting species and subtype families. Although most children were infected with Cryptosporidium hominis, there was a cross-reactive antibody response to C. parvum antigen. These results support further development of p23 as a vaccine candidate.

Genetic diversity of Cryptosporidium spp. from Bangladeshi children.

The genetic diversity of Cryptosporidium spp. from infected children was characterized for the first time in Bangladesh. Seven C. hominis and C. parvum subtype families (including a new family, IIm) and 15 subtypes (including 2 new subtypes) were identified. The dominance of specific families and subtypes was different from that in other countries.

Single-dose azithromycin for the treatment of cholera in adults.

BACKGROUND: Single-dose azithromycin is effective in the treatment of severe cholera in children, but its effectiveness in adults has not been evaluated. METHODS: We conducted a double-blind, randomized trial comparing the equivalence of azithromycin and ciprofloxacin (each given in a single 1-g dose of two 500-mg tablets) among 195 men with severe cholera caused by Vibrio cholerae O1 or O139. Patients were hospitalized for five days. A stool culture was performed daily. Primary outcome measures were clinical success (the cessation of watery stools within 48 hours after drug administration) and bacteriologic success (the inability to isolate V. cholerae after 48 hours). RESULTS: Therapy was clinically successful in 71 of 97 patients receiving azithromycin (73 percent) and in 26 of 98 patients receiving ciprofloxacin (27 percent) (P<0.001) and bacteriologically successful in 76 of 97 patients receiving azithromycin (78 percent) and in 10 of 98 patients receiving ciprofloxacin (10 percent) (P<0.001). Patients who were treated with azithromycin had a shorter duration of diarrhea than did patients treated with ciprofloxacin (median, 30 vs. 78 hours); a lower frequency of vomiting (43 percent vs. 67 percent); fewer stools (median, 36 vs. 52); and a lower stool volume (median, 114 vs. 322 ml per kilogram of body weight). The median minimal inhibitory concentration of ciprofloxacin for the 177 isolates of V. cholerae O1 was 0.25 mug per milliliter, which was 11 to 83 times as high as that in previous studies at this site. CONCLUSIONS: Single-dose azithromycin was effective in the treatment of severe cholera in adults. The lack of efficacy of ciprofloxacin may result from its diminished activity against V. cholerae O1 strains currently circulating in Bangladesh. (ClinicalTrials.gov number, NCT00229944.).

Single-dose ciprofloxacin versus 12-dose erythromycin for childhood cholera: a randomised controlled trial.

BACKGROUND: Single-dose ciprofloxacin is effective for the treatment of severe cholera in adults. We assessed whether single-dose ciprofloxacin would be as effective as 3-day, 12-dose erythromycin in achieving clinical cure in children with severe cholera. METHODS: We did a randomised, open label, controlled trial in children age 2-15 years with V cholerae O1 or O139 present in stool on dark-field microscopy. Children received either a single 20 mg/kg dose of ciprofloxacin (n=90) or 12.5 mg/kg of erythromycin (n=90) every 6 h for 3 days, and remained in hospital for 5 days. The primary outcome was clinical success of treatment, defined as cessation of watery stools within 48 h of start of drug treatment. Analysis was per protocol. This study is registered with the ClinicalTrials.gov Protocol Registration System at http://www.clinicaltrials.gov (registration number NCT 00142272) [corrected] FINDINGS: Of 180 children randomised 162 completed the study. Treatment was clinically successful in 60% (47/78) of children treated with ciprofloxacin and in 55% (46/84) of those treated with erythromycin (difference 5% [95% CI -10 to 21]). Children receiving ciprofloxacin vomited less often (58%vs 74%; difference 16% [2 to 30]), had fewer stools (15 vs 21; 6 [0 to 9]), and less stool volume (152 vs 196 mL/kg; 43 mL/kg [13 to 87]) than those receiving erythromycin. Bacteriological failure was more common in ciprofloxacin-treated patients (58%vs 30%; 28% [13 to 43]) than erythromycin-treated patients. INTERPRETATION: Single-dose ciprofloxacin achieves clinical outcomes similar to, or better than, those achieved with 12-dose erythromycin treatment in childhood cholera, but is less effective in eradicating V cholerae from stool.