74Subclinical atrial fibrillation before and after acute medical illness or noncardiac surgery: insights from ASSERT

OnBehalf

ASSERT Investigators

Background

Atrial fibrillation (AF) is frequently detected perioperatively or during acute medical illness. It is unclear if such AF is reversible and unlikely to recur, or is a manifestation of paroxysmal AF.

Objective

To compare the prevalence of pacemaker-detected, subclinical AF (atrial rate >190 bpm) before and after hospitalization for noncardiac surgery or medical illness in patients without a history of clinical AF.

Methods

ASSERT enrolled patients who were >65 years old and had hypertension but no known AF. Pacemakers and defibrillators recorded episodes of subclinical AF. We identified participants who were hospitalized for noncardiac surgery or medical illness, and created heart rhythm profiles, centred on the day of hospitalization. We compared the prevalence of subclinical AF before and after hospitalization. We blanked the 30 days before hospitalization, because of uncertainty in defining the precise onset of illness.

Results

Among 2580 patients, 436 had a documented surgical or medical hospitalization. In the 30 days following a first hospitalization, 43 patients (9.9%) had >1 episode of >6 minutes of subclinical AF; 20 (4.6%) had >6 hours and 13 (3%) had >24 hours.

A higher proportion of patients had >1 episode of subclinical AF >6 minutes in the 30 days following a first surgical or medical hospitalization, as compared to the period between 30 and 60 days before hospitalization (9.9% versus 4.4%, P < 0.001). There was no significant difference when comparing 0-90 days after hospitalization to 30-120 days before (13.7% versus 10.6%, P = 0.1). Similar results were observed for the same comparisons with episodes >6 hours (4.6% versus 2.3%, P = 0.03 and 5.9% versus 5.6%, P = 0.8, respectively).

The majority of patients with subclinical AF in the 30 days following hospitalization had at least one episode of subclinical AF of the same duration in the 6 months prior (50% for episodes >6 minutes; 69% for >6 hours and 60% for >24 hours). Those who did have subclinical AF in the 30 days following hospitalization were more likely to have had subclinical AF in the past 6 months than those who did not (OR 7.2 95%CI 3.2-15.8 for episodes >6 minutes; OR 32.6, 95%CI 10.3-103.4 for >6 hours and OR 36.3 95%CI 9.0-146.0 for >24 hours).

Conclusions

The prevalence of subclinical AF increased following hospitalization for noncardiac surgery or medical illness.  However, most patients with subclinical AF following hospitalization had previously experienced similar episodes, particularly those with longer episodes of subclinical AF.

Return of esophageal function after treatment for achalasia as determined by impedance-manometry

BACKGROUND

Treatment for achalasia is aimed at the lower esophageal sphincter (LES), although little is known about the effect, if any, of these treatments on esophageal body function (peristalsis and clearance). We sought to measure the effect of various treatments using combined manometry (peristalsis) with Multichannel Intraluminal Impedance (MII) (esophageal clearance).

METHODS

We enrolled 56 patients with Achalasia referred to the University of Washington Swallowing Center between January 2003 and January 2006. Each was grouped according to prior treatment: 38 were untreated (untreated achalasia), 10 had undergone botox injection or balloon dilation (endoscopic treatment), and 16 a laparoscopic Heller myotomy. The preoperative studies for 8 of the myotomy patients were included in the untreated achalasia group. Each patient completed a dysphagia severity questionnaire (scale 0-10). Peristalsis was analyzed by manometry and esophageal clearance of liquid and viscous material by MII.

RESULTS

Mean dysphagia severity scores were significantly better in patients after Heller Myotomy than in either of the other groups (2.0 vs. 5.3 in the endoscopic group and 6.5 in untreated achalasia, p < 0.05). Peristaltic contractions were observed in 63% of patients in the Heller myotomy group, compared with 40% in the endoscopic group and 8% in untreated achalasia (p < 0.05 for both treatment groups vs. untreated achalasia). Liquid clearance rates were significantly better in both treatment groups: 28% in Heller myotomy and 16% in endoscopic treatment compared to only 5% in untreated achalasia (p < 0.05). Similarly, viscous clearance rates were 19% in Heller myotomy and 11% in endoscopic treatment, vs. 2% in untreated achalasia (p < 0.05). In the subset of patients who underwent manometry/MII both pre- and postoperatively, peristalsis was observed more frequently postoperatively than in preop studies (63% of patients exhibiting peristalsis vs. 12%), as was complete clearance of liquid (35% of swallows vs. 14%) and viscous boluses (22% of swallows vs. 14%). These differences were not significant, however. In the patients who had a myotomy the return of peristalsis correlates with effective esophageal clearance (liquid bolus: r = 0.46, p = 0.09 and viscous bolus: r = 0.63, p < 0.05). There is no correlation between peristalsis and bolus clearance in the endoscopic treatment group.

CONCLUSIONS

With treatment Achalasia patients exhibit some restoration in peristalsis as well as improved bolus clearance. After Heller Myotomy, the return of peristalsis correlates with esophageal clearance, which may partly explain its superior relief of dysphagia.

Decreased bone mineral density in the pediatric renal transplant population

All renal transplant recipients at our centre have had bone mineral density assessment (BMD) by DEXA scans of their lumbar spine while on the transplant waitlist and at 6-month intervals post-transplant over the past 7 yr. Risk factors for osteopenia and osteoporosis including donor source, dialysis status prior to transplantation, prior renal disease, and biopsy confirmed rejection events and their relationship to BMD of the lumbar spine were assessed. Thirty-nine children transplanted over the past 7 yr were included in this study. In total, 127 BMD longitudinal assessments were performed. From 1990 to 1997, ATG/ALG was used as antibody induction therapy. From 1997 to 2002, Basiliximab was utilized. Cyclosporin A (CyA) was the primary immunosuppressant for most children with tacrolimus as primary (n = 2) and switch for CyA failure or toxicity (n = 16). Prednisone was administered at a dose of 1 mg/kg/day for the first week and tapered to 10 mg/m2/alternate day by 1 month post-transplant. Azathioprine 1.5 mg/kg/day was continued for 1 yr and discontinued in children who were rejection free. All rejections were biopsy confirmed and treated with a prednisone pulse. Using a repeated measures regression analysis, we have found that L1-L4 BMD z score is affected by height and transplant number. It is also related to time relative to transplant in a quadratic fashion. There was an inverse relationship between advancing patient age and L1-L4 BMD z score. L1-L4 BMD z score was not related to weight, pre-existing renal disease, gender, donor source, type of renal replacement therapy prior to transplantation, or rejection events.

Insulin-independent, MAPK-dependent stimulation of NKCC activity in skeletal muscle

Na(+)-K(+)-Cl(-) cotransporter (NKCC) activity in quiescent skeletal muscle is modest. However, ex vivo stimulation of muscle for as little as 18 contractions (1 min, 0.3 Hz) dramatically increased the activity of the cotransporter, measured as the bumetanide-sensitive (86)Rb influx, in both soleus and plantaris muscles. This activation of cotransporter activity remained relatively constant for up to 10-Hz stimulation for 1 min, falling off at higher frequencies (30-Hz stimulation for 1 min). Similarly, stimulation of skeletal muscle with adrenergic receptor agonists phenylephrine, isoproterenol, or epinephrine produced a dramatic stimulation of NKCC activity. It did not appear that stimulation of NKCC activity was a reflection of increased Na(+)-K(+)-ATPase activity because insulin treatment did not stimulate NKCC activity, despite insulin's well-known stimulation of Na(+)-K(+)-ATPase activity. Stimulation of NKCC activity could be blocked by pretreatment with inhibitors of mitogen-activated protein kinase (MAPK) kinase 1/2 (MEK1/2) activity, indicating that activation of the extracellular signal-regulated kinase 1/2 (ERK1/2) MAPKs may be required. These data indicate a regulated NKCC activity in skeletal muscle that may provide a significant pathway for potassium transport into skeletal muscle fibers.

Unique 5'-end of a Na(+)-K(+)-2Cl- cotransporter-like mRNA expressed in rat skeletal muscle

Functional evidence presented by others indicates that rat slow-twitch skeletal muscle lacks typical Na(+)-K(+)-2Cl- cotransporter activity, as determined by loop diuretic-sensitive potassium transport. This report presents a unique 5' mRNA sequence of a Na(+)-K(+)-2Cl- cotransporter-like molecule expressed in the rat soleus muscle and the deduced N-terminus of the protein. In addition to its unique 5' mRNA sequence, the coding region of the N-terminus is quite short compared with other known Na(+)-K(+)-2Cl- cotransporters. Nonetheless, the mRNA possesses conserved cotransporter-like membrane spanning domains, though one domains corresponding to a reported exon is divergent. Therefore, it appears that skeletal muscle does express a Na(+)-K(+)-2Cl- cotransporter-like mRNA that may code for a protein with atypical Na(+)-K(+)-2Cl- cotransporter properties.

Molecular and functional evidence for Na(+)-K(+)-2Cl(-) cotransporter expression in rat skeletal muscle

Doubt has been raised about the expression of a functional Na(+)-K(+)-2Cl(-) cotransporter in rat skeletal muscle. In this study we present molecular and functional evidence for expression of a protein having the characteristics of a cotransporter. RT-PCR of RNA isolated from rat soleus muscle with primers to a conserved putative membrane-spanning domain resulted in a single product of predicted size. Sequencing of the product showed that it bears >90% homology with known rodent NKCC1 (BSC2) cotransporters. RNase protection assay of RNA isolated from the rat soleus muscle also identified this sequence. Immunologic detection of the cotransporter with two different antibodies indicated the presence of cotransporter protein, perhaps more than one, in blots of total muscle protein. Immunohistochemical detection by confocal microscopy localized the majority of expression of the protein to the muscle fibers. Functional studies of cotransport activity also indicate the appropriate sensitivity to inhibitors and ion dependence. Taken together, these data support the presence and function of Na(+)-K(+)-2Cl(-) cotransporter activity in the soleus muscle of the rat.

Validation of color Doppler measurements of minimum patent ductus arteriosus diameters: significance for coil embolization

BACKGROUND

Echocardiography is sometimes performed to identify candidates for coil embolization of patent ductus arteriosus (PDA). Therefore we attempted to determine the validity of color Doppler echocardiography to accurately determine the minimum PDA diameter.

METHODS AND RESULTS

We reviewed data from 27 children (median 3.8 years, range 1 to 15 years) with PDAs and measured their minimum ductal diameters by color flow Doppler echocardiography and by angiography. We found that there were significant mean differences between the color Doppler and angiographic measurements (2.7+/-0.8 vs 1.6+/-0.7 mm, P< .001) with color Doppler exceeding angiographic measurements by > or = 1.0 mm in 15 (56%) of 27 patients. More importantly, color Doppler measured a PDA > or = 4.0 mm (usually greater than that recommended for coiling) in 3 (11%) patients in whom the angiographic measurement was <4.0 mm. Correlation analysis demonstrated no correlation between the color Doppler and angiographic measurements (r2 = 0.17, P= .04, SEE = 0.2 mm).

CONCLUSIONS

These data suggest that color Doppler echocardiography often overestimates the true minimum PDA diameter, therefore we recommend that a color Doppler-based recommendation that a PDA is too large for transcatheter coil occlusion not be used exclusively to exclude a patient from this treatment modality.

Division of the main pulmonary artery: suboptimal palliation for the patient with a univentricular heart

We describe a patient in whom a thrombus formed in the distal main pulmonary artery stump after a bidirectional Glenn procedure with division of the main pulmonary artery and in whom a restrictive inlet ventricular septal defect also developed. These findings emphasize the importance of maintaining antegrade flow through the pulmonary trunk and providing dual sources of ventricular outflow with a Damus-Kaye-Stansel anastomosis in patients with a univentricular heart without pulmonary stenosis.

Noncompaction of the ventricular myocardium in Melnick-Needles syndrome

A 4-year-old asymptomatic boy was referred for evaluation after being diagnosed with Melnick-Needles syndrome. Echocardiography demonstrated noncompaction of the left ventricular myocardium as an isolated cardiac finding. Though other structural cardiac defects were reported previously in this syndrome, this is the first report of this rare cardiac anomaly in this likewise rare syndrome. We postulate that this occurrence represents a primary disorder of early fetal development. Patients with Melnick-Needles syndrome should be evaluated for noncompaction of the ventricular myocardium and its potential cardiovascular dysfunction.

Dose-volume considerations with linear programming optimization

A method of incorporating dose-volume considerations within the framework of conventional linear programming is presented. This method is suitable for the optimization of beam weights and angles using a conformal treatment philosophy (i.e., tailoring the high-dose region to the target volume only). Dose-volume constraints are introduced using the concept that volumes of normal tissue nearer the target volume will be allowed higher dose constraints than volumes of normal tissue distal to the target volume. Each involved normal structure is divided into high-dose and low-dose volumes. These two volume partitions are represented by constraint points with either high-dose or low-dose constraints, respectively. Optimized treatment plans for three clinical sites demonstrate that this technique meets or surpasses the original dose-volume constraints for a conformal-type treatment plan using straightforward linear programming in a time frame that is comparable to other linear programming problems.