Low Intensity Epicardial Pacing During the Absolute Refractory Period Augments Left Ventricular Function Mediated by Local Catecholamine Release.

BACKGROUND: Biventricular epicardial (Epi) pacing can augment left ventricular (LV) function in heart failure. We postulated that these effects might involve catecholamine release from local autonomic nerve activation. To evaluate this hypothesis we applied low intensity Epi electrical stimuli during the absolute refractory period (ARP), thus avoiding altered activation sequence. METHODS: Anesthetized pigs (n = 6) were instrumented with an LV pressure (LVP) transducer, left atrial (LA) and LV Epi pacing electrodes, and sonomicrometer segment length (SL) gauges placed proximal and remote to the LV stimulation site. A catheter was placed into the great cardiac vein adjacent to the LV pacing site for norepinephrine (NE) analysis. During LA pacing at constant rate, 3 pulses (0.8 milliseconds, 2-3x threshold) were applied to the LV Epi electrodes during the ARP. An experimental run consisted of baseline, stimulation (10 minutes), and recovery (5 minutes), repeated 3 times before and after ß1 - receptor blockade (BB, metoprolol). RESULTS: ARP stimulation produced significant increases in cardiac function reflected by elevated LVP, LV, dP/dtmax , and reduced time to LV dP/dtmax . This was accompanied by increased coronary NE levels and increases in LVP versus SL loop area in the remote myocardial segment. In contrast, the proximal segment exhibited early shortening and decreased loop area. BB abolished the changes in SL and LV function despite continued NE release. CONCLUSION: These results demonstrate that ARP EPI stimulation induces NE release mediating augmented global LV function. This effect may contribute to the beneficial effect of biventricular Epi pacing in heart failure in some patients.

Stiff left atrial syndrome after catheter ablation for atrial fibrillation: clinical characterization, prevalence, and predictors.

BACKGROUND: There have been no studies of atrial diastolic function after catheter ablation of atrial fibrillation (AF). We encountered a few patients with symptomatic left atrial (LA) diastolic dysfunction and associated pulmonary hypertension (PH) that developed after catheter ablation for atrial fibrillation. Similar findings were described in patients after cardiac surgery and were referred to as the "stiff left atrial syndrome." OBJECTIVE: The purpose of this study was to prospectively quantify the incidence of patients developing PH associated with diastolic hemodynamic abnormalities of the LA after radiofrequency ablation of AF and to identify the possible predictors. METHODS: Between January 2009 and July 2010, data on 1,380 consecutive patients were prospectively collected. Before ablation and at follow-up, all patients had an echocardiogram to assess for the presence of PH. Patients with no echocardiographic evidence of PH but complaining of unexplained dyspnea with LA diastolic abnormalities were evaluated with right heart catheterization (RHC). Patients were included in the analysis if they developed new or worsening PH postablation with evidence of LA diastolic dysfunction by RHC or direct LA pressure measurement. All patients were evaluated for pulmonary vein stenosis and excluded if this condition was identified. RESULTS: The mean age was 62 ± 11 (75% male), and nonparoxysmal AF was the predominant arrhythmia (71%). New or worsening PH with associated LA diastolic abnormalities was detected in 19 (1.4%) patients after ablation. The prevalence of PH did not differ between AF types (P = .612). Compared with patients who did not develop PH, LA scarring (P <.001), diabetes (P = .026), and obstructive sleep apnea (OSA; P = .006) were more frequently observed among those who developed PH. In a multivariable logistic model, preprocedure LA size ≤45 mm (odds ratio [OR] = 6.13; P = .033), mean LA pressure (OR 1.14; P = .025), severe LA scarring (OR = 4.4; P = .046), diabetes mellitus (OR = 9.5; P = .004), and OSA (OR = 6.2; P = .009) were independently associated with the development of PH postablation. CONCLUSIONS: After radiofrequency catheter ablation of atrial fibrillation (RFCAF), PH with LA diastolic dysfunction or the so-called stiff LA syndrome is a rare but potentially significant complication of AF ablation. Severe LA scarring, LA ≤45 mm, diabetes mellitus, OSA, and high LA pressure are clinical variables that predict the development of this syndrome. The main clinical findings include dyspnea, congestive heart failure, PH, and large V waves on pulmonary capillary wedge pressure (PCWP) or LA pressure tracings in the absence of mitral regurgitation.

Salvage of pacemakers and automatic implantable cardioverter-defibrillators using dermis grafts.

BACKGROUND: Thin patients with thoracic pacemakers and automatic implantable cardioverter-defibrillators often have minimal tissue over the devices, with erosion through the surface a major concern. This erosion can lead to device infection and need for removal, or primary device infection can, in turn, lead to erosion. Even worse is exposure and infection of the leads to the heart, with fatalities having occurred. Pressure symptoms, as with shoulder seatbelt straps, can occur, and the visible deformity may be objectionable. METHODS: To correct these problems without device removal, we used a novel surgical approach. Thirteen patients had 15 grafts, of either the acellular dermal graft AlloDerm (LifeCell Corp, Branchburg, NJ [n = 13 for threatened exposure or pressure symptoms, including two repeats]) or autogenous dermis (n = 2 for existing open wounds with chronic drainage) placed over the devices. RESULTS: After all graft procedures, there was no skin breakdown; exposure and extrusion were completely prevented. Follow-up was 3 to 68 months (mean 36.8). The 2 open wound patients treated with dermis autografts had no recurrence of wound breakdown. Most patients with pressure symptoms had reduction in tenderness and pain. Patients liked the visible softening of the device contour, but not the subtly increased forward projection. The only immediate complication was one rapidly expanding hematoma leading to graft removal. One late complication was a mild infection, treated successfully. CONCLUSIONS: Acellular human dermal allografts, or live dermis autografts, provided significant protection over cardiac pacing devices in 13 patients with 15 grafts, with no subsequent surface exposures or extrusions.