RR interval variability in the evaluation of ventricular tachycardia and effects of implantable cardioverter defibrillator therapy.

BACKGROUND: An implantable cardioverter defibrillator (ICD) is the most reliable therapeutic device for preventing sudden cardiac death in patients with sustained ventricular tachycardia (VT). Regarding its effectiveness, targeted VT is defined based on the tachyarrhythmia cycle length. However, variations in RR interval variability of VTs may occur. Few studies have reported on VT characteristics and effects of ICD therapy according to the RR interval variability. We aimed to identify the clinical characteristics of VTs and ICD therapy effects according to the RR interval variability. METHODS: We analyzed 821 VT episodes in 69 patients with ICDs or cardiac resynchronization therapy defibrillators. VTs were classified as irregular when the difference between two successive beats was >20 ms in at least one of 10 RR intervals; otherwise, they were classified as regular. We evaluated successful termination using anti-tachycardia pacing (ATP)/shock therapy, spontaneous termination, and acceleration between regular and irregular VTs. The RR interval variability reproducibility rates were evaluated. RESULTS: Regular VT was significantly more successfully terminated than irregular VT by ATP. No significant difference was found in shock therapy or VT acceleration between the regular and irregular VTs. Spontaneous termination occurred significantly more often in irregular than in regular VT cases. The reproducibility rates of RR interval variability in each episode and in all episodes were 89% and 73%, respectively. CONCLUSIONS: ATP therapy showed greater effectiveness for regular than for irregular VT. Spontaneous termination was more common in irregular than in regular VT. RR interval variability of VTs seems to be reproducible.

Superior Rhythm Discrimination With the SmartShock Technology Algorithm　- Results of the Implantable Defibrillator With Enhanced Features and Settings for Reduction of Inaccurate Detection (DEFENSE) Trial.

BACKGROUND: Shocks delivered by implanted anti-tachyarrhythmia devices, even when appropriate, lower the quality of life and survival. The new SmartShock Technology®(SST) discrimination algorithm was developed to prevent the delivery of inappropriate shock. This prospective, multicenter, observational study compared the rate of inaccurate detection of ventricular tachyarrhythmia using the SST vs. a conventional discrimination algorithm.Methods and Results:Recipients of implantable cardioverter defibrillators (ICD) or cardiac resynchronization therapy defibrillators (CRT-D) equipped with the SST algorithm were enrolled and followed up every 6 months. The tachycardia detection rate was set at ≥150 beats/min with the SST algorithm. The primary endpoint was the time to first inaccurate detection of ventricular tachycardia (VT) with conventional vs. the SST discrimination algorithm, up to 2 years of follow-up. Between March 2012 and September 2013, 185 patients (mean age, 64.0±14.9 years; men, 74%; secondary prevention indication, 49.5%) were enrolled at 14 Japanese medical centers. Inaccurate detection was observed in 32 patients (17.6%) with the conventional, vs. in 19 patients (10.4%) with the SST algorithm. SST significantly lowered the rate of inaccurate detection by dual chamber devices (HR, 0.50; 95% CI: 0.263-0.950; P=0.034). CONCLUSIONS: Compared with previous algorithms, the SST discrimination algorithm significantly lowered the rate of inaccurate detection of VT in recipients of dual-chamber ICD or CRT-D.

Coronary Artery Disease Screening With Carotid Ultrasound Examination by a Primary Care Physician.

BACKGROUND: In this study, we investigated the feasibility of primary care physicians using carotid ultrasound to perform coronary artery disease screening in asymptomatic patients with multiple coronary risk factors. METHODS: We retrospectively collected the data of 135 consecutive asymptomatic patients (mean age: 68.5 ± 8.4 years; male, 75%) who were referred to our institution due to abnormal findings on a carotid ultrasound performed by a primary care physician and who underwent coronary computed tomography angiography. RESULTS: The mean number of risk factors was 4.1 ± 1.2 and the mean intima-media thickness was 2.00 ± 0.63 mm. Mild (≤ 50%), moderate (51-75%), and severe (> 76%) coronary stenosis was observed in 54 (40%), 27 (20%), and 25 patients (19%), respectively, while no plaque was found in 24 patients (18%), and five patients (4%) could not be evaluated due to calcification. Consequently, coronary angiography was performed in 56 (41%) patients and coronary intervention was required in 31 patients (23%). A multivariate logistic regression analysis demonstrated that the ratio of low-density lipoprotein cholesterol levels to high-density lipoprotein cholesterol levels, the use of calcium channel blockers and the value of the diastolic blood pressure were related to > 50% coronary stenosis. CONCLUSIONS: The use of carotid ultrasound in the coronary artery disease screening by primary care physicians resulted in a high prevalence of coronary artery disease and high probabilities of coronary angiography and revascularization, and thus it is considered to be a useful and feasible strategy for the screening of asymptomatic patients.

Heart rate control with single administration of a long-acting ß-blocker at bedtime before coronary computed tomography angiography.

BACKGROUND: Beta-blockers are used to control the heart rate prior to coronary computed tomography (CT) angiography. However, in-hospital administration is time-consuming, and it is hard to decrease the heart rate to <60 beats per minute (bpm) when the initial heart rate is increased. In this study, we examined whether the single administration of long-acting ß-blocker at bedtime before angiography is effective for achieving the target heart rate. METHODS AND RESULTS: A total of 314 consecutive patients with a resting heart rate >60bpm who underwent coronary CT angiography were retrospectively collected. Either bisoprolol or atenolol was orally administered the night before to 166 patients (beta group), and no additional medication was administered to the other 148 patients (control group). When the heart rate was >60bpm on arrival, a ß-blocker or verapamil was orally administered at the discretion of the physician. Although the baseline heart rate was not significantly different between the groups, the ß-blocker treatment the night before significantly reduced the heart rate compared to control group upon arrival at the hospital and at the time of angiography. The rate of achievement of a heart rate ≤60bpm on arrival at the hospital was significantly higher in the beta group, and even after the additional treatment. CONCLUSIONS: Bedtime administration of a long-acting ß-blocker the night before coronary CT angiography is an effective option to achieve the target heart rate at the time of examination.

Blackout during meals: A case report of swallow syncope due to sinus arrest.

A 79-year-old male, with a history of percutaneous coronary intervention (PCI), was referred to our cardiovascular department for a detailed examination of blackout caused by sinus arrest only during meals. Ultrasound echocardiography showed normal cardiac contraction with no asynergy, irrespective of the remaining stenotic coronary lesion. An electrophysiological study revealed deteriorated atrioventricular nodal conduction at a Wenckebach point of 70 beats per minute. However, sinus node function was normal as demonstrated by a sinus node recovery time of 1369 ms. Coronary angiography showed triple-vessel disease including the remaining stenotic coronary lesion, and a PCI was performed on the right coronary artery. Nevertheless, sinus arrest during meals was unchanged. Swallow syncope was partially improved by dietary modification; however, pacemaker implantation (PMI) was performed eventually, and the patient became asymptomatic after PMI. .

Resolution of a left ventricular thrombus by the thrombolytic action of dabigatran.

A 77-year-old man was referred to our cardiovascular department for detailed examination after abnormal electrocardiography findings were obtained during a preoperative cataract surgery workup. Ultrasound echocardiography (UCG) and computed tomography (CT) revealed evidence of previous myocardial infarction with anteroseptal akinesis and a left ventricular (LV) thrombus (14 × 12 mm). Dabigatran (220 mg/day) was prescribed as an outpatient treatment, and the disappearance of the LV thrombus was confirmed by UCG and CT 27 days after dabigatran initiation. No thromboembolism occurred between treatment initiation and thrombus resolution. Our results indicate that dabigatran has thrombolytic action on an acute pre-existing intracardiac thrombus.

Ventricular pacing inhibition by oversensing due to diaphragmatic myopotential during deep inspiration.

An 80-year-old man, who had dilated cardiomyopathy with right ventricular (RV) dilatation, underwent implantable cardioverter defibrillator (ICD) implantation for advanced atrioventricular block and primary prevention of sudden cardiac death. Tined and screw-in leads were placed on the right atrial appendage and RV apex, respectively. Ventricular pacing inhibition was detected after surgery due to oversensing by diaphragmatic myopotential occurring only during deep inspiration. We performed re-surgery and switched the screw-in lead for a tined lead. The diaphragmatic myopotential decreased, thereby improving oversensing by diaphragmatic myopotential and ventricular pacing inhibition. It might be beneficial to use a tined lead when placing the ventricular lead at the RV apex for implantation of a pacemaker or ICD if oversensing of diaphragmatic myopotential is observed using a screw-in lead. .

A severely calcified neointima 9 years after bare metal stent implantation.

An increasing number of studies have reported intimal atherosclerotic changes, or neoatherosclerosis in the late phase after bare metal stent implantation, however, only a few reports have showed the presence of severe intimal calcification in a bare metal stent. We herein report a case of a 68-year-old male with severely calcified neointima occurring 9 years after the bare metal stent implantation. Pre-procedural coronary computed tomography angiography and peri-procedural intravascular ultrasound demonstrated severe calcification within the in-stent restenotic lesion. Although the pre-dilation balloon ruptured due to the calcification, the lesion was nevertheless successfully dilated with the stent. Calcified lesions often require complex techniques, and we therefore should be aware of the potential occurrence of a severely calcified neointima in coronary stents, and performing coronary computed tomography angiography in advance is a great help for performing effective coronary intervention.

Acute effects of isosorbide dinitrate and nicorandil on the coronary slow flow phenomenon.

BACKGROUND: Microvascular dysfunction has been proposed as the most likely mechanism of the coronary slow flow phenomenon (CSFP). OBJECTIVES: To determine the effects of isosorbide dinitrate and nicorandil on the CSFP. METHODS: Changes in thrombolysis in myocardial infarction (TIMI) frame count following the intracoronary administration of isosorbide dinitrate and nicorandil were assessed in 11 patients with the CSFP. RESULTS: After the administration of isosorbide dinitrate, the median TIMI frame count decreased to 32 (range 20-60) [p = 0.003], which was lower than that of the control [43 (29-73)]. The count decreased further to 25 (12-34) [p = 0.041] after the administration of nicorandil. The count after the subsequent administration of contrast medium was increased to 32 (20-49) [p = 0.03]. CONCLUSIONS: These angiographic findings indicate that the intracoronary administration of nicorandil is superior to isosorbide dinitrate with regard to improving the CSFP. These findings suggest that microvascular spasm is the main factor in the pathogenesis of the CSFP.