Red cell membrane stiffness in iron deficiency

The purpose of this study was to characterize red blood cell (RBC) deformability by iron deficiency. We measured RBC deformability to ektacytometry, a laser diffraction method for determining the elongation of suspended red cells subjected to shear stress. Isotonic deformability of RBC from iron-deficient human subjects was consistently and significantly lower than that of normal controls. In groups of rats with severe and moderate dietary iron deficiency, RBC deformability was also reduced in proportion to the severity of iron deficiency. At any given shear stress value, deformability of resealed RBC ghosts from both iron-deficient humans and rats was lower than that of control ghosts. However, increase of applied shear stress resulted in progressive increase in ghost deformation, indicating that ghost deformability was primarily limited by membrane stiffness rather than by reduced surface area-to-volume ratio. This was consistent with the finding that iron-deficient cells had a normal membrane surface area. In addition, the reduced mean corpuscular hemoglobin concentration (MCHC) and buoyant density of the iron-deficient rat cells indicated that a high hemoglobin concentration was not responsible for impaired whole cell deformability. Biochemical studies of rat RBC showed increased membrane lipid and protein crosslinking and reduced intracellular cation content, findings that are consistent with in vivo peroxidative damage. RBC from iron-deficient rats incubated in vitro with hydrogen peroxide showed increased generation of malonyldialdehyde, an end-product of lipid peroxidation, compared to control RBC. Taken together, these findings suggest that peroxidation could contribute in part to increased membrane stiffness in iron- deficient RBC. This reduced membrane deformability may in turn contribute to impaired red cell survival in iron deficiency.     

Occlusion of the Modified Blalock–Taussig Shunt: Unique Methods of Treatment and Review of Catheter‐based Intervention

Objective. To report unique methods of treatment and review catheter‐based intervention for occluded modified Blalock–Taussig shunts (BTS). Methods. Case reports and articles involving children undergoing catheter‐based treatment for occluded modified BTS were reviewed. Results. Literature review detailed 38 patients in whom occluded modified BTS were treated with 39 catheter‐based interventions. Thrombolytics alone were delivered by catheter in 13 cases. Balloon angioplasty was performed in 23 cases, 5 with stent implantation. Both thrombolytic delivery and angioplasty were performed in 3 cases, 2 with stent implantation. Intervention was initially successful at re‐establishing modified BTS patency in 35/39 (90%) of cases. Patency could not be established in 2 patients who then proceeded to the operating for surgical shunt revision. Two deaths occurred during the procedures. Three cases at Emory University demonstrate uncommon or unique instances of catheter‐based intervention: (1) declotting of a shunt in a patient supported by extracorporeal membrane oxygenation (ECMO); (2) declotting of a shunt via a right axillary arterial approach; and (3) declotting of a shunt using a carotid arterial (ECMO) cannula for percutaneous access. Conclusions. The use of catheter‐based techniques for the treatment of BTS occlusion is highly successful, and potentially avoids high‐risk re‐operative intervention. ECMO can provide for a stable patient during the procedure. Hopefully, with improved technology and innovative procedures, more children in the future with BTS occlusion can be served by successful percutaneous intervention.     

Different degrees of risk of high-frequency atrial fibrillation in symptomatic and asymptomatic WPW syndrome. Electrophysiologic evaluation

Sudden death in WPW pattern can occur when atrial fibrillation (a.f.) with rapid ventricular response develops. This event seems to be the final result of three concomitant conditions: the appearance of an orthodromic atrio-ventricular reciprocating tachycardia, the most common form of tachycardia in these patients; a high atrial vulnerability, which makes possible that reciprocating tachycardia degenerates into atrial fibrillation and a short anterograde refractory period of the Kent bundle. With the purpose of evaluating the risk to develop high frequency a.f., 36 WPW subjects were electrophysiologically studied. 22 were symptomatic for palpitations (Group I) and 14 were totally asymptomatic (Group II). 3/22 patients of Group I had experienced clinical atrial fibrillation (Subgroup I A), which was never documented in the remaining 19/22 (Subgroup I B). In all cases the following parameters were analyzed: the presence or absence of the retrograde conduction of the anomalous pathway, essential for the occurrence of orthodromic reciprocating atrio-ventricular tachycardia; the presence or absence of a high atrial vulnerability and the presence of RR intervals between pre-excited complexes during induced a.f. less than 250 msec. As an index of atrial vulnerability were considered the spontaneous degeneration into atrial fibrillation of an electrophysiologically induced reciprocating tachycardia and/or the induction of a sustained a.f. by programmed right atrial stimulation during sinus rhythm and/or during 600 and 400 ms atrial driving and/or by 160-250/m' atrial bursts. Results--Retrograde conduction of Kent bundle was documented in 100% of Gr. I vs 22% of Gr. II (p less than 0.001).(ABSTRACT TRUNCATED AT 250 WORDS)     

Comparative assessment of right, left, and biventricular pacing in patients with permanent atrial fibrillation.

AIMS: Left ventricular (LV) and biventricular (BiV) pacing are potentially superior to right ventricular (RV) apical pacing in patients undergoing atrioventricular (AV) junction ablation and pacing for permanent atrial fibrillation. METHODS AND RESULTS: Prospective randomized, single-blind, 3-month crossover comparison between RV and LV pacing (phase 1) and between RV and BiV pacing (phase 2) performed in 56 patients (70+/-8 years, 34 males) affected by severely symptomatic permanent atrial fibrillation, uncontrolled ventricular rate, or heart failure. Primary endpoints were quality of life and exercise capacity. Compared with RV pacing, the Minnesota Living with Heart Failure Questionnaire (LHFQ) score improved by 2 and 10% with LV and BiV pacing, respectively, the effort dyspnoea item of the Specific Symptom Scale (SSS) changed by 0 and 2%, the Karolinska score by 6 and 14% (P<0.05 for BiV), the New York Heart Association (NYHA) class by 5 and 11% (P<0.05 for BiV), the 6-min walked distance by 12 (+4%) and 4 m (+1%), and the ejection fraction by 5 and 5% (P<0.05 for both). BiV pacing but not LV pacing was slightly better than RV pacing in the subgroup of patients with preserved systolic function and absence of native left bundle branch block. Compared with pre-ablation measures, the Minnesota LHFQ score improved by 37, 39, and 49% during RV, LV, and BiV pacing, respectively, the effort dyspnoea item of the SSS by 25, 25, and 39%, the Karolinska score by 39, 42, and 54%, the NYHA class by 21, 25, and 30%, the 6-min walking distance by 35 (12%), 47 (16%), and 51 m (19%) and the ejection fraction by 5, 10, and 10% (all differences P<0.05). CONCLUSIONS: Rhythm regularization achieved with AV-junction ablation improved quality of life and exercise capacity with all modes of pacing. LV and BiV pacing provided modest or no additional favourable effect compared with RV pacing.     

Ablation of perimitral flutter following catheter ablation of atrial fibrillation: impact on outcomes from a randomized study (PROPOSE)

MVI Block vs Trigger Ablation in PMFL . Introduction: Patients with previous ablation for atrial fibrillation (AF) may experience recurrence of perimitral flutter (PMFL). These arrhythmias are usually triggered from sources that may also induce AF. This study aims at determining whether ablation of triggers or completing mitral valve isthmus (MVI) block prevents more arrhythmia recurrences. Methods and Results: Sixty‐five patients with recurrent PMFL after initial ablation of long standing persistent AF were included in this study. Thirty‐two patients were randomized to MVI ablation only (Group 1) and 33 were randomized to cardioversion and repeat pulmonary vein (PV) isolation plus ablation of non‐PV triggers (Group 2). MVI bidirectional block was achieved in all but 1 patient from Group 1. In Group 2, reconnection of 17 PVs was detected in 14 patients (42%). With isoproterenol challenge, 44 non‐PV trigger sites were identified in 28 patients (85%, 1.57 sites per patient). At 18‐month follow‐up, 27 patients (84%) from Group 1 had recurrent atrial tachyarrhythmias, of whom 15 remained on antiarrhythmic drug (AAD); however, 28 patients from Group 2 (85%, P < 0.0001 vs Group 1) were free from arrhythmia off AAD. The ablation strategy used in Group 2 was associated with a lower risk of recurrence (hazard ratio = 0.10, 95% CI 0.04–0.28, P < 0.001) and an improved arrhythmia‐free survival (log rank P < 0.0001). Conclusion: In patients presenting with PMFL after ablation for longstanding persistent AF, MVI block had limited impact on arrhythmia recurrence. On the other hand, elimination of all PV and non‐PV triggers achieved higher freedom from atrial arrhythmias at follow‐up. (J Cardiovasc Electrophysiol, Vol. 23, pp. 137‐144, February 2012)