Brian L. Cmolik

Salvage of Infected ICDs: Management Without Removal

During the 7‐year period from August 1986 to December 1993, 242 patients with malignant ventricular arrhythmias underwent 242 ICD implantations and 50 subcutaneous generator changes. Wound infections developed in 5 patients (1.7%): in 3 cases, after primary implantation (3/242 [1,2%]); and in 2 following a generator change (2/50 [4.0%]). This difference was not statistically significant. Infection developed at the generator pocket and became clinically manifest between 6 weeks and 40 months, postoperatively. Our treatment approach with the first patient consisted of simple debridement of the pocket and reimplantation of the existing generator. This led to recurrence, and the generator was safely explanted. In the remaining four patients, our approach has been that of local treatment, with wide debridement of the pocket, and placement of a closed irrigation system with continuous irrigation with a bacitracin, polymyxin, neomycin solution, and culture‐specific antibiotic therapy. We have successfully controlled the infection and salvaged the generator with this approach in all four patients, who are all alive and well at a mean follow‐up of 25.0 ± 17.3 months with no recurrence. The good results obtained in these patients suggest that the concept of total explantation of the infected ICD should be reassessed.

Cost analysis of early extubation after coronary bypass surgery

BACKGROUNDnAlthough early extubation after coronary bypass surgery has been shown to reduce length of stay, a systematic cost analysis of its economic benefit has not been reported, and previous studies have used hospital charges that are typically confused with actual costs.nnnMETHODSnA consecutive series of 690 patients undergoing coronary bypass surgery during a 24-month period were studied to determine the effect of early extubation, defined as removal of the endotracheal tube within 8 hours of arrival to the intensive care unit, on length of stay and hospital costs. Patients in group 2 (n = 362) who underwent coronary bypass surgery in 1995, subsequent to the initiation of an early extubation protocol, were compared with those in group 1 (n = 328) operated on in 1994, before implementation of early extubation. To reflect true hospital resource consumption, only costs (not charges) directly related to patient health core (variable direct cost) were analyzed.nnnRESULTSnBaseline characteristics such as age, gender, previous myocardial infarctions, ejection fraction, reoperations, diabetes, and left main stenosis were similar in both groups. Operative mortality for the entire group was 3.3% and did not differ between the two groups; the incidence of serious morbidity was 10.9% for the entire group. Early extubation was accomplished in 38% of patients in group 2 versus 3% in group 1 (p < 0.001), and postoperative length of stay declined from 9.4 days to 7.7 days (p < 0.01). This was accompanied by a significant (p = 0.001) reduction in variable direct cost per case.nnnCONCLUSIONSnEarly extubation after coronary bypass surgery is an effective strategy of reducing length of stay and does not appear to impact on either morbidity or mortality. An additional benefit is significant cost savings realized through accelerated recovery and control of resource use.

Risk analysis of coronary bypass surgery after acute myocardial infarction

BACKGROUNDnCurrent strategies for management of acute myocardial infarction (MI) include thrombolysis, angioplasty, and coronary bypass surgery singly or in combination. This study was designed to identify contemporary risk factors for coronary bypass surgery among patients in this high-risk group.nnnMETHODSnBetween June 1992 and December 1995, 1181 consecutive patients underwent isolated coronary bypass surgery. Of these, 316 underwent coronary bypass surgery within 21 days of MI. Mean age was 65 years (range, 33 to 87 years), and 73% were male. There were 166 patients with stable angina (group 1), 107 patients with unstable angina requiring intravenous nitroglycerin for a control of ischemia (group 2), 20 patients with angina requiring intraaortic balloon counterpulsation for stabilization (group 3), and 23 patients with severe postinfarction ischemia complicated by cardiogenic shock (group 4).nnnRESULTSnThe overall in-hospital mortality rate was 5.1% (16 of 316), which was higher (p < 0.05) than the 2.5% (22 of 865) among patients undergoing coronary bypass surgery without recent myocardial infarction. Mortality increased with severity of clinical preoperative status and was 1.2% in group 1, 3.7% in group 2, 20.0% in group 3, and 26% in group 4. Serious postoperative morbidity occurred in 7.3% of patients. Multivariate logistic regression analysis identified preoperative intraaortic balloon counterpulsation, left ventricular dysfunction, and renal insufficiency as the only independent correlates of mortality.nnnCONCLUSIONSnCoronary bypass surgery can be safely performed in stable patients at any time after acute MI, with an operative mortality similar to elective surgery. Thus, in this era of medical cost containment, there is no apparent indication for prolonged stabilization attempts that delay surgery.

A versatile microprocessor-based multichannel stimulator for skeletal muscle cardiac assist

A versatile, microprocessor-based stimulator for skeletal muscle cardiac assist (SMCA) has been designed, constructed, and used in several studies. The stimulator uses multiple bipolar electrodes to deliver arbitrarily specified electrical stimulus sequences to three nerve branches of the latissimus dorsi muscle. The electrodes are electrically isolated to effect regional stimulation of the muscle. The width, amplitude, and interpulse interval of each pulse in the stimulus sequence are independently variable, and the three channels are independently programmable, allowing a wide variety of stimulus patterns. Battery powered units have been used in studies for up to one year. In this paper, the stimulator and sample applications in SMCA are described.

Successful atrial defibrillation with very-low-energy shocks by means of temporary epicardial wire electrodes

Sustained atrial fibrillation is very common after cardiac surgical procedures. We hypothesized that atrial defibrillation could be accomplished consistently and safely by means of low-energy shocks delivered by temporary stainless steel wire electrodes placed at the time of the operation. Sterile pericarditis was created in five mongrel dogs (20.9 +/- 2.1 kg), and pairs of standard temporary stainless steel wire electrodes were placed on the right atrial appendage, on Bachmanns bundle, and on the right ventricular apex for pacing, sensing, and recording. Temporary stainless steel wire electrodes, insulated except for the distal 6 cm and used to deliver defibrillation shocks, were placed adjacent to both atrial free walls and secured to the pericardium. All electrodes were brought out through the skin, and the sternotomy was closed. Dogs were tested in the conscious state on postoperative day 2. Sustained atrial fibrillation was induced by rapid atrial pacing. A customized software program was used to control the defibrillator, which delivered R wave-synchronous biphasic shocks to the atria through the temporary defibrillation electrodes. The shock intensity began at 50 volts and was increased by 10-volt increments until atrial fibrillation was terminated. Atrial fibrillation was terminated in all dogs at 112 +/- 7 volts, with an energy of 0.42 +/- 0.07 joule and an impedance of 67.8 +/- 4 ohms (all values mean +/- standard error of the mean). The mean percent success for atrial defibrillation at this minimal threshold was 49%. Thus at low-threshold voltages atrial fibrillation could be terminated with every other shock. A 25% increase in the minimal threshold voltage improved the conversion rate to 73% (mean energy 0.66 +/- 0.19 joule and mean impedance of 67 +/- 3.8 ohms). No complications were detected with the use of the electrodes or after their removal on the seventh postoperative day. One instance of electrode migration on the right atrial free wall was detected by roentgenography, but this did not adversely affect atrial defibrillation threshold. No ventricular arrhythmias or hemodynamic complications were noted during shock delivery. We conclude that successful conversion of atrial fibrillation to sinus rhythm can be achieved consistently with shock energies below 0.5 joule delivered with temporary epicardial defibrillation wire electrodes in this canine pericarditis model. These results suggest that this approach to the management of sustained atrial tachyarrhythmias has considerable promise in the management of atrial fibrillation in patients who have had cardiac operations.

Cardioprotection by St. Thomas’ solution is mediated by protein kinase C and tyrosine kinase

BACKGROUNDnIntracellular signaling pathways, specifically the activation of protein kinase C and tyrosine kinase, are essential to the cardioprotection of ischemic preconditioning. We proposed that activation of PKC and TK contribute to the myocardial protection of St. Thomas No. 2 cardioplegia solution (STC).nnnMATERIALS AND METHODSnIsolated rat hearts were exposed to 40 min of global ischemia followed by 120 min of reperfusion. Before ischemia, hearts received no treatment (control; n = 7), STC (n = 7), phorbol 12-myristate 13-acetate (PMA; n = 6), PMA + chelerythrine (n = 6), anisomycin (n = 6), anisomycin + genistein (n = 7), STC + chelerythrine (n = 7), STC + genistein (n = 7), PMA + genistein (n = 7) or anisomycin + chelerythrine (n = 7). Left ventricular developed pressure (LVDP) recovery, myocardial infarct size, and lactate dehydrogenase release were measured.nnnRESULTSnSTC as well as PMA (protein kinase C activator) and anisomycin (tyrosine kinase activator) significantly reduced infarct size (6.9 +/- 2.9%, 9.6 +/- 2.1%, 14.0 +/- 4.4%) compared with controls (42.4 +/- 2.9%, P < 0.05). The infarct reduction of PMA and anisomycin were blocked by their inhibitors chelerythrine and genistein, respectively. Both chelerythrine (29.2 +/- 4.1%, P < 0.05) and genistein (40.4 +/- 4.3%, P < 0.05) attenuated the reduction of infarct size provided by STC. The recovery of LVDP improved with STC, PMA and anisomycin (72.6 +/- 1.4%, 60.4 +/- 4.7%, 57.2 +/- 4.6%) compared with control (33.8 +/- 3.6%, P < 0.05). Addition of chelerythrine or genistein to STC impaired recovery of LVDP (52.3 +/- 4.4%, 35.1 +/- 2.5%, P < 0.05) compared with STC treatment.nnnCONCLUSIONnAdministration of the pharmacologic inhibitors chelerythrine and genistein blunts the cardioprotection caused by STC treatment.

Increased coronary artery blood flow with aortomyoplasty in chronic heart failure

BACKGROUNDnWe hypothesized that diastolic counter-pulsation using aortomyoplasty will increase coronary blood flow.nnnMETHODSnIn dogs (n = 6, 20 to 25 kg), the left latissimus dorsi muscle was isolated, wrapped around the descending thoracic aorta, and conditioned by chronic electrical stimulation. Heart failure was induced by rapid ventricular pacing. In a terminal study, left ventricular and aortic pressures, and blood flow in the left anterior descending coronary artery and descending aorta were measured. The endocardial-viability ratio was calculated.nnnRESULTSnAortomyoplasty increased mean diastolic aortic pressure (70 +/- 5 to 75 +/- 5 mm Hg, p < 0.05) and reduced peak left ventricular pressure (86 +/- 4 to 84 +/- 4 mm Hg, p < 0.05), leading to a 16% increase in endocardial-viability ratio (1.29 +/- 0.05 to 1.49 +/- 0.05, p < 0.05). Coronary blood flow was increased by 15% (8.2 +/- 1.5 to 9.4 +/- 1.6 mL/min, p < 0.05). During muscle contraction, 2.7 +/- 0.5 mL was ejected from the wrapped aortic segment.nnnCONCLUSIONSnThese data demonstrate that aortomyoplasty provides successful diastolic counterpulsation after muscle conditioning and heart failure.

Unusual Cause of Acute Mitral Regurgitation: Idiopathic Hypereosinophilic Syndrome

Idiopathic hypereosinophilic syndrome (HES) is a rare multisystem condition characterized by dysregulated overproduction of eosinophils. Cardiac involvement in HES is characterized by necrosis from infiltration of eosinophils and thrombus formation and, in the late stage, by fibrosis and chronic valvular regurgitation. We report a very unusual presentation of idiopathic HES with acute mitral regurgitation due to papillary muscle rupture. The transesophageal echocardiogram was suggestive of a flail posterior leaflet and suspicious for endocarditis. Intraoperatively, papillary muscle rupture was seen and the patient underwent mitral valve replacement. The pathologic examination of the valve revealed eosinophilic infiltration of the papillary muscle. The patient was treated with steroids and responded well clinically.

Optimizing muscle wrap orientation for aortomyoplasty

A new surgical approach to augment the pumping ability of failed hearts is known as aortomyoplasty-a technique in which the latissimus dorsi muscle is wrapped around the aorta and stimulated during cardiac diastole to provide chronic diastolic counterpulsation. The authors hypothesized that the manner in which the latissimus dorsi muscle is wrapped around the aorta will determine the amount of augmentation during counterpulsation. In dogs (n=9), they measured the cardiovascular effects of different muscle wrap techniques. Their results suggest that muscle wrap orientation determines the amount of augmentation during aortomyoplasty, and a new muscle wrap technique provides greater augmentation than wrap techniques previously reported.