Implantation of leadless pacemakers via inferior vena cava filters is feasible and safe: Insights from a multicenter experience.

BACKGROUND: The leadless Micra transcatheter-pacing system (Micra-TPS) is implanted via a femoral approach using a 27-French introducer sheath. The Micra Transcutaneous Pacing Study excluded patients with inferior vena cava (IVC) filters. OBJECTIVE: To examine the feasibility and safety of Micra-TPS implantation through an IVC filter. METHODS: This multicenter retrospective study included patients with an IVC filter who underwent a Micra-TPS implantation. Data for clinical and IVC filter characteristics, preprocedure imaging, and procedural interventions were collected. The primary outcome was a successful leadless pacemaker (LP) implantation via a femoral approach in the presence of an IVC filter. Periprocedural and delayed clinical complications were also evaluated. RESULTS: Of the 1528 Micra-TPS implants attempted, 23 patients (1.5%) had IVC filters. The majority (69.6%) of IVC filters were permanent. Six (26.1%) patients underwent preprocedural imaging to assess for filter patency. One patient's filter was retrieved before LP implantation. The primary outcome was achieved in 21 of 22 patients (95.5%) with an existing IVC filter. An occluded IVC precluded LP implantation in one patient. Difficulty advancing the stiff guidewire or the 27-Fr sheath was encountered in five patients. These cases required repositioning of the wire (n = 2), gradual sheath upsizing (n = 2), or balloon dilation of the filter (n = 1). Postprocedure fluoroscopy revealed intact filters in all cases. During a median 6-month follow-up, there were no clinical complications related to the filter or the Micra-TPS. CONCLUSION: This multicenter experience demonstrates the feasibility and safety of Micra-TPS implantation via an IVC filter without acute procedural or delayed clinical complications.

The shortage of short QT intervals.

BACKGROUND: Syncope or sudden death has been associated with a short QT interval (QTc, < 300 ms), the so-called short QT syndrome. The current prevalence of this syndrome is unknown. The aim of this study was to evaluate the prevalence of short QT intervals (ie, QTc, < 300 ms) in a general hospital population. METHODS: We retrospectively queried 479,120 consecutive ECGs that had been archived (Marquette MAC 5000 Resting ECG System; GE Healthcare; Boston, MA) over a 16-year period. We examined the distribution of QT intervals in our population from 150 randomly selected ECGs with normal findings, excluding patients who had been receiving medications known to prolong the QT interval. RESULTS: From 1988 to 2004, 479,120 ECGs from 106,432 patients were analyzed, which reported 215 tracings with a QTc of < 300 ms. Each ECG was then measured manually, and no QTc of < 300 ms was validated (67% were found to be in error because of a pacemaker artifact, 17% showed supraventricular tachycardia with inaccurate detection of the T-wave offset, and 16% were found to have an error in the cycle length calculation). Therefore, not one of the 106,432 patients was found to have a QTc of < 300 ms. The mean QTc (+/- SD) was 430 +/- 19 ms (95% confidence interval, 392 to 468 ms). The QTc of < 300 ms would then reflect > 5 SDs shorter than the mean QTc. CONCLUSIONS: The short QTc reported by an ECG computer was inaccurate and required manual correction. Short QT syndrome, defined as a QTc of < or = 300 ms, is rare. We were unable to find one patient among a population > 100,000 patients with a true QTc of < 300 ms.

Clonic focal seizure of the foot secondary to nonketotic hyperglycemia.

Focal epileptic seizures can be the first manifestation of a diabetic disorder. Metabolic disturbances, including hyperglycemia, mild hyperosmolality, hyponatremia, and lack of ketoacidosis contribute to the development of partial focal seizures. A review of the medical literature for partial focal seizures is presented, followed by a case study of a patient who developed clonic seizures of the right foot secondary to hyperglycemia, hyponatremia, and hyperosmolality.

Left ventricular endocardial pacing: a transarterial approach.

INTRODUCTION: We tested the feasibility of a new technique of direct left ventricular endocardial lead placement across the aortic valve in a chronic (six month) pig model. The potential for aortic valve damage, systemic embolization, and pacing lead maturation and function within the left ventricle are unknown. METHODS: Ten minipigs were successfully implanted with a transaortic left ventricular lead (Medtronic CapSureFix, Minneapolis, MN, USA) placed in the left ventricular apex via the carotid artery. Each pig received either a polyurethane (n = 5) or silicone (n = 5) lead. Post implant each pig received clopidogrel and aspirin for seven days. After six months all surviving pigs underwent thorough necropsy. RESULTS: Each pig had adequate sensing (12.1 +/- 4 mV) and pacing thresholds (0.79 +/- 0.2 @ 0.5 V) at implant. Postoperatively two pigs died of a respiratory illness. One pig died postoperatively due to sepsis. At the six-month follow-up, all surviving pigs (n = 7) were in a healthy state. Of the pigs without dislodgement (n = 5) there was adequate sensing, but a rise in pacing thresholds. Echocardiography revealed a normal ejection fraction and only trace to mild aortic insufficiency in all pigs. Of the seven surviving pigs there were no thromboembolic events noted. One silicone lead was noted to have thrombosis along the lead screw and shaft. CONCLUSION: Direct transaortic placement of a left ventricular lead is feasible. After six months, there was no significant aortic regurgitation and no evidence of thromboembolism despite no anticoagulation. Lead function was acceptable and only one silicone lead (and no polyurethane lead) was noted to have significant thrombosis.

Electrocardiographic T- and U-wave discordance.

BACKGROUND: Abundant information has been reported regarding the U wave, which almost entirely has been focused on U waves in isolation. There has been little investigation of discordant T and U waves. METHODS: Of 18,750 consecutively recorded electrocardiograms, 143 patients were categorized resulting in three groups. Group A: 53 patients with negative T waves and positive U waves (Type I Discordance); Group B: 26 patients with positive T waves and negative U waves (Type II Discordance); and Group C: 63 patients with negative T and negative U waves. Each patient's chart was reviewed for relevant clinical, laboratory, and medical history. RESULTS: Coronary disease was slightly more common in Group A (64%) than in Group B (46%) (P = 0.174; ns). Coronary disease in Group C was extremely common (88%; P <0.001). Hypertension in the two discordant groups was similar: Group A (60%) versus Group B (58%) (P = ns), Group C was significantly higher (88%) (P <0.001). Left ventricular hypertrophy was 49% in Group A and 58% in Group B (P = ns), but Group C was significantly higher at 70% (P = 0.038). CONCLUSIONS: This appears to be the first investigation of the associations of discordant T and U waves. We found that the significance of any U wave is not independent of their respective T wave. In addition, we propose that the U wave not be analyzed in isolation, but rather with respect to its T wave.