Comparison Between Contact Force Monitoring and Unipolar Signal Modification as a Guide for Catheter Ablation of Atrial Fibrillation

Background:

Both contact force monitoring (CFM) and unipolar signal modification (USM) are guides for ablation, which improve the efficacy of pulmonary vein isolation of atrial fibrillation. We sought to compare the outcomes of atrial fibrillation ablation guided by CFM or USM.

Methods:

A total of 136 patients with paroxysmal atrial fibrillation underwent a circumferential pulmonary vein isolation using CF sensing ablation catheters and were randomly assigned to undergo catheter ablation guided by either CFM (CFM-guided group: n=70) or USM (USM-guided group: n=66). In the USM-guided group, each radiofrequency application lasted until the development of completely positive unipolar electrograms. In the CFM-guided group, a CF of 20 g (range, 10–30 g) and minimum force-time integral of 400 g were the targets for each radiofrequency application. The primary end point was freedom from any atrial tachyarrhythmia recurrence without antiarrhythmic drugs at 12-months of follow-up.

Results:

The cumulative freedom from recurrences at 12-months was 85% in the USM-guided group and 70% in the CFM-guided group ( P =0.031). The incidence of time-dependent and ATP-provoked early electrical reconnections between the left atrium and PVs, procedural time, fluoroscopic time, and average force-time integral, did not significantly differ between the 2 groups. The radiofrequency time for the pulmonary vein isolation was shorter in the USM-guided group than CFM-guided group but was not statistically significant ( P =0.077).

Conclusions:

USM was superior to CFM as an end point for radiofrequency energy deliveries during the pulmonary vein isolation in patients with paroxysmal atrial fibrillation in terms of the 12-month recurrence-free rate.

Clinical Trial Registration:

URL: https://www.umin.ac.jp/ctr/index.htm . Unique identifier: UMIN000021127.

Catheter ablation of atrial fibrillation in patients with severely impaired left ventricular systolic function

Little is known about the outcome of catheter ablation of atrial fibrillation (AF) in patients with heart failure (HF) and a severely reduced left ventricular ejection fraction (LVEF). We aimed to clarify the effectiveness of catheter ablation of AF in patients with a severely low LVEF. This retrospective study included 18 consecutive patients with HF and an LVEF of ≤ 35 % who underwent catheter ablation of AF. We investigated the clinical parameters, echocardiographic parameters and the incidence of hospitalizations for HF. During a median follow-up of 21 months (IQR, 13-40) after the final procedure (9 with repeat procedures), 11 patients (61 %) maintained sinus rhythm (SR) (6 with amiodarone). The LVEF and NYHA class significantly improved at 6 months after the CA in 12 patients (67 %) who were in SR or had recurrent paroxysmal AF (from 25.8 ± 6.3 to 37.0 ± 11.7 %, P = 0.02, and from 2.3 ± 0.5 to 1.5 ± 0.7, P < 0.01, respectively) but not in patients who experienced recurrent persistent AF. The patients with SR or recurrent paroxysmal AF had significantly fewer hospitalizations for HF than those with recurrent persistent AF after the AF ablation (log-rank test; P < 0.01). Catheter ablation of AF improved the clinical status in patients with an LVEF of ≤ 35 %. A repeat ablation procedure and amiodarone were often necessary to obtain a favorable outcome.

EFFECT OF DECELERATED FERMENTATION ON MORPHOLOGY AND MECHANICAL PROPERTIES OF NATURAL RUBBER LATEX

Decelerated fermentation of natural rubber latex was performed to investigate the relationship between the morphology and mechanical properties of natural rubber. Natural rubber latex was preserved with sodium hydroxymethylglycinate, as a bactericide, to decelerate the fermentation of nonrubber components such as proteins, phospholipids, carbohydrate, and so forth. Gradual increases in the viscosity of the latex and gel content of the resulting rubber took place as the preservation period was prolonged, which were distinguished from less change in the viscosity of high-ammonia natural rubber (HANR) and high gel content of its rubber. The particle size distribution was dramatically changed during decelerated fermentation, although that of the HANR latex did not change. The pH and nitrogen content of the rubbers were independent of the preservation time. Morphology of the fermented natural rubber and the HANR was observed with scanning probe microscopy. Fewer mechanical properties of the fermented natural rubber were related to the destruction of the nanomatrix structure of the nonrubber components, which resulted from the decrease in the fatty acid ester groups with bacteria as compared with the good mechanical properties of the HANR.

Localized reentrant tachycardia in the aorta contiguity region mimicking perimitral atrial flutter in the context of atrial fibrillation ablation

We describe a case with a focal atrial tachycardia (AT) masquerading as perimitral atrial flutter revealed after circumferential pulmonary vein antral isolation for atrial fibrillation. It was successfully terminated and became noninducible by a point ablation on the left atrial anterior wall (LAAW) near the mitral annulus in contact with the aortic root and on the left superior pulmonary vein-left atrial appendage ridge, without any linear ablation, using electroanatomical mapping and conventional precise mapping with a maximum amplified gain within the low-voltage area. The AT revealed in our case was an LAAW-aorta contiguity area-related AT.

Gender difference in baroreflex sensitivity to predict cardiac and cerebrovascular events in type 2 diabetic patients

BACKGROUND

Cardiovascular autonomic neuropathy is a major complication in patients with diabetes mellitus (DM), and baroreflex sensitivity (BRS) reportedly can predict cardiovascular prognosis in type 2 DM patients. The hypothesis that cardiovascular events are associated with gender differences in BRS was tested in the present study.

METHODS AND RESULTS

From 1998, we have evaluated BRS by phenylephrine methods in 185 consecutive type 2 DM patients. The long-term prognostic value of BRS was compared between 91 female (5812 years) and 94 male patients (5811 years). There was no significant difference in age or severity and duration of DM between the 2 groups. When compared to male, the BRS value in female patients was significantly lower (9.266.0 vs. 5.975.0 ms/mmHg, P < 0.0001). During a mean of 62.7 months of follow-up, 16 female patients developed cardiovascular events (17.6%) including stroke, acute myocardial infarction, angina pectoris requiring percutaneous coronary intervention or coronary artery bypass grafting and congestive heart failure requiring admission, while only 4 male patients developed events (4.3%, P < 0.005). In females, the Kaplan-Meier curves revealed that those with depressed BRS (< 6 ms/mmHg) had a higher incidence of cardiovascular events than those with preserved BRS (P < 0.05), but this relationship was not observed in male patients.

CONCLUSIONS

Although the reason why females had a more depressed BRS remains unclear, our findings demonstrated that a depressed BRS value can accurately predict cardiovascular events, especially in female patients with type 2 DM.

Baroreflex sensitivity predicts cardiovascular events in patients with type 2 diabetes mellitus without structural heart disease

BACKGROUND

Cardiovascular autonomic neuropathy is a major complication in patients with diabetes mellitus (DM). However, the relationship between cardiovascular autonomic neuropathy and the incidence of cardiovascular events has been poorly investigated in type 2 DM. The present study aimed to assess the long-term cardiovascular predictive value of baroreflex sensitivity (BRS) in Japanese patients with type 2 DM without structural heart disease.

METHODS AND RESULTS

BRS was evaluated using the phenylephrine method in 210 patients with type 2 DM who did not have structural heart disease or other severe complications. BRS was considered depressed if <6 ms/mmHg. Accurate follow-up information for 3-10 years (mean 4.7 years) was obtained in 184 patients (90 females, 94 males; mean age 58+/-12 years). The initial onset of a major adverse cardiovascular event (MACE) was investigated. During follow-up, 19 patients presented with a MACE (4 cardiovascular deaths, 3 nonfatal myocardial infarctions, 4 coronary revascularizations, 5 strokes, 2 congestive heart failures). Cox proportional hazards regression analysis revealed that depressed BRS was independently associated with the incidence of MACE (hazard ratio 1.93, 95% confidence interval 1.09-3.82, P=0.0236).

CONCLUSIONS

Depressed BRS at baseline has long-term cardiovascular predictive value in Japanese patients with type 2 DM without structural heart disease.

Induction of heat shock proteins prevents the arrhythmogenic substrate for atrial fibrillation

Atrial fibrillation (AF) is the commonest arrhythmia. Studies have shown that atrial tachypacing (artificial persistent AF) causes electrical remodelling. This is characterised by the shortening of the atrial effective refractory period (ERP), in which reduction in L-type Ca(2+) channel current plays an essential part. Atrial fibrosis, a feature of structural remodelling, is induced by continuous infusion of angiotensin II, and has been associated with conduction delay in atria, which promotes AF. Acute atrial ischaemia, frequently observed during development of acute coronary syndrome, has been associated with atrial conduction heterogeneity, which also promotes AF. Induction of heat shock proteins (Hsp72 and Hsp27) by hyperthermia and/or geranylgeranylacetone has demonstrated to protect the heart against such atrial remodelling. The potent protective role of Hsp72 and Hsp27 against clinical AF in patients who underwent open heart surgery has been shown. Taken together, interventions that induce heat shock responses (including induction of Hsp72 and Hsp27) may prevent newly developed AF and delay the progression of paroxysmal AF to persistent AF.

Hyperthermia treatment prevents angiotensin II-mediated atrial fibrosis and fibrillation via induction of heat-shock protein 72

We tested the hypothesis that atrial fibrosis and atrial fibrillation (AF) evoked by angiotensin II (AII) could be prevented by the induction of heat-shock protein 72 (HSP72) by hyperthermia (HT). In cultured atrial fibroblasts isolated from male Sprague-Dawley rats, HT (42 degrees C) was applied for 30 min. AII (100 nmol/L) was added to the medium 8 h later. HT induced the expression of HSP72, which was associated with the attenuation of AII-induced extracellular signal-regulated kinase (ERK1/ERK2) phosphorylation, alpha-smooth muscle actin (alpha-SMA) expression, transforming growth factor-beta(1) secretion, collagen synthesis, and expression of collagen type I and tissue inhibitor of metalloproteinases-1. A small interfering RNA targeting HSP72 abolished these anti-fibrotic effects of HT. In male Sprague-Dawley rats in vivo, an osmotic mini-pump was subcutaneously implanted for continuous infusion of AII (400 ng/kg/min). Whole-body HT (43 degrees C, 20 min) was applied 24 h before and 7, 14, and 21 days after the start of the AII infusion. Repeated HT led to the induction of HSP72 expression, which resulted in an attenuation of AII-induced left atrial fibrosis. In an electrophysiological study using isolated perfused heart, continuous AII caused slowing of interatrial conduction without affecting atrial refractoriness. In AII-treated hearts, extrastimuli from the right atrial appendage resulted in a high incidence of repetitive atrial responses, which were suppressed by treatment with HT. Our results suggest that HT treatment is effective in suppressing AII-mediated atrial fibrosis and AF via induction of HSP72 at least in parts, and is thus expected to be a novel strategy for prevention of AF.

Mitochondria are targets for geranylgeranylacetone-induced cardioprotection against ischemia-reperfusion in the rat heart

It has been shown that orally administered geranylgeranylacetone (GGA), an anti-ulcer drug, induces expression of heat shock protein 72 (HSP72) and provides protection against ischemia-reperfusion in rat hearts. The underlying protective mechanisms, however, remain unknown. Mitochondria have been shown to be a selective target for heat stress-induced cardioprotection. Therefore, we hypothesized that preservation of mitochondrial function, owing to an opening of a putative channel in the inner mitochondrial membrane, the mitochondrial ATP-sensitive potassium (mitoK(ATP)) channel, could be involved in GGA- or heat stress-induced cardioprotection against ischemia-reperfusion. Rats were treated with oral GGA or vehicle. Twenty-four hours later, each heart was isolated and perfused with a Langendorff apparatus. GGA-treated hearts showed better functional recovery, and less creatine kinase was released during a 30-min reperfusion period, after 20 min of no-flow ischemia. Concomitant perfusion with 5-hydroxydecanoate (5-HD, 100 microM) or glibenclamide (10 microM) abolished the GGA-induced cardioprotective effect. GGA also showed preserved mitochondrial respiratory function, isolated at the end of the reperfusion period, which was abolished with 5-HD treatment. GGA prevented destruction of the mitochondrial structure by ischemia-reperfusion, as shown by electron microscopy. In cultured cardiomyocytes, GGA induced HSP72 expression and resulted in less damage to cells, including less apoptosis in response to hypoxia-reoxygenation. Treatment with 5-HD abolished the GGA-induced cardioprotective effects but did not affect HSP72 expression. Our results indicate that preserved mitochondrial respiratory function, owing to GGA-induced HSP72 expression, may, at least in part, have a role in cardioprotection against ischemia-reperfusion. These processes may involve opening of the mitoK(ATP) channel.

Effects of insulin resistance on geranylgeranylacetone-induced expression of heat shock protein 72 and cardioprotection in high-fat diet rats

We investigated the effects of insulin resistance on the expression of heat-shock proteins (HSPs) and myocardial protection against ischemia/reperfusion injury. Male Sprague-Dawley rats received normal chow (CNT) or high-fat (HiF) diet. HiF diet for 6 weeks resulted in the development of insulin resistance, which was evaluated by oral glucose test and insulin tolerance test. Twenty-four hour after oral administration of geranylgeranylacetone (GGA) (200 mg/kg), the heart was isolated and perfused retrogradely with two different doses of insulin (0.1 or 1 mU/ml). Myocardial expression of HSP72 was examined using Western blot analysis. In the HiF group, the expression of HSP72 in response to GGA was decreased. The recovery of left ventricular developed pressure (LVDP) 30 min after reperfusion was tended to be lower in HiF group than in CNT group. Although GGA improved the recovery of LVDP in both CNT and HiF rats, LVDP during reperfusion period was significantly lower in HiF group than in CNT group. High-dose insulin perfusion caused deterioration of post-ischemic functional recovery and LVDP was not different between the two groups, but GGA-induced cardioprotection was preserved irrespective of the dose of insulin both in the CNT and HiF rats. This is the first demonstration that expression of HSP72 was depressed in the heart and that reduced HSP72 was related with less cardioprotection against ischemic insult in high-fat diet-induced insulin resistance rats.

Selenium deficiency in a patient with Crohn's disease receiving long-term total parenteral nutrition

We report a case of selenium deficiency in a patient with Crohn's disease on long-term total parenteral nutrition (TPN). She manifested lassitude of the legs, discoloration of the nail beds, and macrocytosis. Since her plasma selenium level was found to be below the measurable level, we diagnosed this case as selenium deficiency. After intravenous administration of sodium selenite, her symptoms were reversed. Careful attention should be paid to selenium deficiency when a patient receives long-term TPN; supplementary administration of selenium via TPN may be required because selenium is often not routinely added to TPN formulations.

A more sensitive and less time-consuming sandwich enzyme immunoassay for insulin in human serum with less serum interference

This paper describes an improved sandwich enzyme immunoassay for insulin in human serum. The detection limit was significantly improved from 0.1 mU/L to 0.02 mU/L, by incubation with guinea-pig anti-insulin Fab'-peroxidase conjugate in the presence of normal guinea-pig F(ab')2 to reduce the non-specific binding of the conjugate. The degree of serum interference was considerably reduced by coating polystyrene balls with acid-treated anti-insulin IgG and by incubating the polystyrene balls with serum samples at a lower temperature for a shorter time. The time for incubation with anti-insulin Fab'-peroxidase conjugate was also shortened. As a result, the volume of serum that could be used increased from 10 microliters to 50 microliters, and the time for immuno-reactions was reduced from 8 h to 4 h. Applicability of the present improvement to enzyme immunoassay of other antigens in human serum is discussed.