Technological and Clinical Challenges in Lead Placement for Cardiac Rhythm Management Devices.

Cardiac disease is a leading cause of death worldwide. Disturbance in the conduction system of the heart may trigger or aggravate heart dysfunction, affecting the efficiency of the heart, and lead to heart failure or cardiac arrest. Patients may require implantable cardiac rhythm management devices (ICRMDs) to maintain or restore the heart rhythm. ICRMDs have undergone important improvements, yet limitations still exist, presenting important technological challenges. Most ICRMDs consist of a subcutaneous control unit and intracardiac electrodes. The leads, which connect the electrodes to the control unit, are usually placed transvenously through the subclavian veins. Various locations inside the heart are used for placement of electrodes, depending on the specific condition. Some of the limitations to effective pacemaker therapy are associated with placement and location of the leads. Various approaches have been developed to overcome these challenges, such as multi-site pacing and leadless solutions. This paper aims to review the state of the art for the selection of placement sites for pacemakers, implantable cardioverter defibrillator (ICD) and cardiac resynchronization therapy devices (CRT) devices and discuss potential technological advancements to improve the results of ICRMD-therapy including development av leadless technology.

Edge density based automatic detection of inflammation in colonoscopy videos.

Colon cancer is one of the deadliest diseases where early detection can prolong life and can increase the survival rates. The early stage disease is typically associated with polyps and mucosa inflammation. The often used diagnostic tools rely on high quality videos obtained from colonoscopy or capsule endoscope. The state-of-the-art image processing techniques of video analysis for automatic detection of anomalies use statistical and neural network methods. In this paper, we investigated a simple alternative model-based approach using texture analysis. The method can easily be implemented in parallel processing mode for real-time applications. A characteristic texture of inflamed tissue is used to distinguish between inflammatory and healthy tissues, where an appropriate filter kernel was proposed and implemented to efficiently detect this specific texture. The basic method is further improved to eliminate the effect of blood vessels present in the lower part of the descending colon. Both approaches of the proposed method were described in detail and tested in two different computer experiments. Our results show that the inflammatory region can be detected in real-time with an accuracy of over 84%. Furthermore, the experimental study showed that it is possible to detect certain segments of video frames containing inflammations with the detection accuracy above 90%.

Myocardial tissue CO2 tension detects coronary blood flow reduction after coronary artery bypass in real-time†.

BACKGROUND: Coronary stenosis after coronary artery bypass grafting (CABG) may lead to myocardial ischaemia and is clinically difficult to diagnose. In a CABG model, we aimed at defining variables that detect hypoperfusion in real-time and correlate with impaired regional ventricular function by monitoring myocardial tissue metabolism. METHODS: Off-pump CABG was performed in 10 pigs. Graft blood flow was reduced in 18 min intervals to 75, 50, and 25% of baseline flow with reperfusion between each flow reduction. Myocardial tissue Pco2 (Pt(CO2)), Po2, pH, glucose, lactate, and glycerol from the graft supplied region and a control region were obtained. Regional cardiac function was assessed as radial strain. RESULTS: In comparison with baseline, myocardial pH decreased during 75, 50, and 25% flow reduction (-0.15; -0.22; -0.37, respectively, all P<0.05) whereas Pt(CO2) increased (+4.6 kPa; +7.8 kPa; +12.9 kPa, respectively, all P<0.05). pH and Pt(CO2) returned to baseline upon reperfusion. Lactate and glycerol increased flow-dependently, while glucose decreased. Regional ventricular contractile function declined significantly. All measured variables remained normal in the control region. Pt(CO2) correlated strongly with tissue lactate, pH, and contractile function (R=0.86, R=-0.91, R=-0.70, respectively, all P<0.001). New conductometric Pt(CO2) sensors were in agreement with established fibre-optic probes. Cardiac output was not altered. CONCLUSIONS: Myocardial pH and Pt(CO2) monitoring can quantify the degree of regional tissue hypoperfusion in real-time and correlated well with cellular metabolism and contractile function, whereas cardiac output did not. New robust conductometric Pt(CO2) sensors have the potential to serve as a clinical cardiac monitoring tool during surgery and postoperatively.

Neurologic recovery after prolonged circulatory arrest in surgery for aortic dissection.

BACKGROUND: Brain injury manifested by subtle, transient neurologic and neuropsychologic dysfunctions occurs in about a quarter of patients who are subjected to periods of deep hypothermia and circulatory arrest (DHCA). We describe a patient who sustained minimal neurologic damage despite prolonged DHCA. METHODS: The patient was a previously healthy 62-year-old woman with acute type A aortic dissection that involved the ascending aorta. During surgery we established retrograde cerebral perfusion and DHCA to provide cerebral protection, and during the procedure the patient underwent 3 separate DHCA periods with a total circulatory arrest time of 91 minutes. Because of tubing damage, retrograde cerebral perfusion was not used during the final period (59 minutes). The patient's head was packed in ice to facilitate maintenance of brain hypothermia. Her average systemic temperature during the third period of circulatory arrest was 22.5 degrees C. RESULTS: Extensive neuropsychologic testing, which was performed to assess the patient's cognitive functions and abilities at 4-month follow-up, showed an absence of global cognitive decline and only a moderate impairment of attentional capacity. Overall cognitive functioning was within the normal range and did not interfere with everyday activities or quality of life. CONCLUSION: Although the total arrest time vastly exceeded the recommended safe period, our patient survived and sustained minimal neurologic damage. The combination of neuroprotective measures used may have contributed to this beneficial outcome.

Partial left ventriculectomy: the 2nd International Registry Report 2000.

BACKGROUND: Partial left ventriculectomy (PLV) has been performed without standardized inclusion or exclusion criteria. METHODS: An international registry of PLV was expanded, updated, and refined to include 287 nonischemic cases voluntarily reported from 48 hospitals in 11 countries. RESULTS: Gender, age, ventricular dimension, etiology, ethnology, myocardial mass, operative variation, presence or absence of mitral regurgitation, and transplant indication had no effects on event-free survival, which was defined as absence of death or ventricular failure that required a ventricular assist device or listing for transplantation. Preoperative patient conditions, such as duration of symptoms (> 9 vs < 3 years; p = 0.001), New York Heart Association (NYHA) class (Class IV vs < Class IV; p = 0.002), depressed contractility (fractional shortening [FS] < 5% vs > 12%; p = 0.001), and refractory decompensation that required emergency procedure (p < 0.001) were associated with reduced event-free survival. Five or more cases in each hospital led to significantly better outcomes than the initial four cases. Rescue procedures for 14 patients nonsignificantly improved patient survival (2-year survival 52%) over event-free survival (2-year survival 48%; p = 0.49), with improved NYHA class among survivors (3.6 to 1.8; p < 0.001). Outcome was better in 1999 than in all series before 1999 (p = 0.02) most likely due to patient selection, which was refined to avoid known risk factors such as reduced proportion of patients in NYHA Class IV, FS < 5%, and hospitals with experience in 10 or less cases. A combination of these risk factors could have stratified 17 high-risk patients with 0% 1-year survival and 26 low-risk patients with 75% 2-year event-free survival. CONCLUSION: Avoidance of risk factors appears to improve survival and might help stratify high- or low-risk patients. Although less symptomatic patients with preserved contractility had better results after PLV, change of indication requires prospective randomized comparison with medical therapies or other approaches.

Improved left ventricular contraction and energetics in a patient with Chagas' disease undergoing partial left ventriculectomy.

A 43-year-old patient with heart failure, precluded from heart transplantation or dynamic cardiomyoplasty because of Chagas' disease cardiomyopathy, mitral regurgitation, and ventricular mural thrombi, underwent mitral valvuloplasty and partial left ventriculectomy (PLV) between the papillary muscles. Intraoperative pressure-volume relationship analyses suggested improvement in left ventricular contraction, energetics, isovolumic relaxation, and mitral valve competency. These improvements allowed prompt, short-term recovery despite unchanged myocardial pathology, which suggests that a surgical approach can alter anatomic-geometric factors and achieve clinical improvement in a dilated failing ventricle.

Histopathology of resected myocardium and outcome of partial left ventriculectomy.

BACKGROUND: Since preoperative hemodynamics are not proven to be a predictor of effects of partial left ventriculectomy (PLV), myocardial histopathology may be better correlated with effects and outcome of PLV. METHODS: Myocyte size (micron) in the excised myocardium was measured in 338 patients undergoing PLV. Endocardial fibrosis, interstitial fibrosis, and inflammatory cell infiltration were enumerated as none = 0, mild = 1, moderate = 2, and severe = 3. These histopathologic observations were correlated with patients' postoperative survival. RESULTS: Reduced survival was seen in patients with advanced (> or = moderate) interstitial fibrosis in all patients (n = 338, p = 0.064) and in the subgroup with nonischemic etiology (n = 229, p = 0.0039). Although correlation between endocardial and interstitial fibrosis was significant (r = 0.55, p < 0.01), endocardial fibrosis failed to correlate with postoperative survival. While Chagas' disease was associated with severe inflammation and poor survival, the presence of inflammatory cell infiltration had no effect on survival in all patients combined (p = 0.943). Although most patients (n = 266, 79%) had myocyte diameter over 30 micron, those with less hypertrophy (< 30 micron, n = 70, 21%) had a tendency toward increased survival (p = 0.067) regardless of underlying etiology. CONCLUSION: Interstitial fibrosis may be an important factor in stratification of patients for repair (PLV) or replacement (transplantation). PLV may be more beneficial in patients with less hypertrophy, before develqpment of interstitial fibrosis. Endomyocardial biopsy might not predict the extent or variation in degree of interstitial fibrosis, which may be better evaluated by other metabolic or perfusion studies that measure overall myocardial histopathology and viability.

Coronary artery exposure in off-pump cabg: a word of caution.

Coronary exposure and stabilization have focal importance in off-pump coronary surgery. Off-pump complete myocardial revascularization can be performed safely in the majority of the patients whenever strict surgical protocols are followed. Although new devices may be used to facilitate the performance of this demanding operation, technical pitfalls should be recognized to ensure the success of the procedure. We herein report our timely experience with the Xpose device (Guidant Corp., Cupertino, CA).

Reoperative coronary artery bypass grafting with and without cardiopulmonary bypass: determinants of perioperative morbidity and mortality.

BACKGROUND: This retrospective study evaluates perioperative results of reoperative coronary artery bypass grafting (CABG) with and without cardiopulmonary bypass (CPB). METHODS: From January 1995 to March 1999 reoperative CABG was performed on 581 patients: 307 (52.84%) patients were operated upon on-CPB and 274 (47.16%) off-CPB. Median sternotomy was used in all patients on-CPB. Median sternotomy or alternative surgical approaches were used in the off-CPB group. Data was retrospectively reviewed. To identify the variables independently related to perioperative mortality and adverse outcome, multivariate analysis was performed in the overall population of 581 patients. RESULTS: Preoperative risk factors were comparable in the two groups. Critical lesions of the right and left circumflex coronary artery were more common in the on-CPB group (p < 0.005). A total of 2.7 grafts/patient was performed in the on-CPB group versus 1.3 grafts/patient in the off-CPB group (p = NS). Freedom from postoperative complications was higher in the off-CPB group (72% versus 90.9%, p < 0.005). Perioperative stroke and respiratory failure rates were more common in the on-CPB group (3.9% versus 0.7% and 5.9% versus 2.2% respectively, p < 0.005). Actual mortality was 5.9% in the on-CPB group and 3.6% in the off-CPB group (p = NS). Risk adjusted mortality was 2.2% and 1.3% in the on-CPB and off-CPB groups respectively. Although CPB was found to be independently related to adverse outcome (odds ratio (OR) = 2.89, p-value < 0.005), no correlation was found between mortality and CPB. CONCLUSIONS: Avoidance of CPB independently reduces adverse outcomes in reoperative CABG without affecting mortality rate.

Does avoidance of cardiopulmonary bypass decrease the incidence of stroke in diabetics undergoing coronary surgery?

BACKGROUND: The adverse effects of diabetes mellitus on the coronary circulation and the higher incidence of cardiovascular events in diabetic patients are well documented [Johnson 1982]. Improvements in myocardial protection, revascularization techniques, and anesthetic management have had favorable impacts on coronary artery bypass grafting (CABG) outcome in diabetic patients. Despite that, diabetic patients are significantly more likely to have a prior history of myocardial infarction, congestive heart failure, peripheral vascular disease, and hypertension, as well as having a significantly greater baseline serum creatinine. The aim of our study was to record, compare, and analyze the stroke rate among patients with a history of preoperative diabetes undergoing "off-pump" CABG (OPCAB) with conventional cardiopulmonary bypass (CPB) CABG to determine whether the stroke rate in this higher risk population could be decreased by off-pump techniques. METHODS: The records of 1,227 patients with a pre-operative history of diabetes undergoing conventional CABG (973 patients, 79.3%) using cardiopulmonary bypass and off-pump CABG 254 (20.7%) were analyzed from 1995 through 1999. There were no differences in age, sex, or elective/urgent status of patients. Preoperative risk factors (gender distribution, carotid disease, ejection fraction, CHF, hypertension, previous MI) were identical in both groups. The goal of the operations were complete revascularization, which was achieved via median sternotomy in both groups. RESULTS: Our reported series reveals a stroke rate of 3.6% in the CPB group and 1.2% in the off-pump group. This evidence alone was not statistically significant, but two other high-risk criteria for stroke, re-do CABG and calcified aortas, revealed that the off-pump series had a higher percentage of each (26.4% redos in off-pump vs. 8.7% CPB redos, p < 0.005; 7.1% calcified aorta cases in the off-pump group vs. 2.9% in the CPB group, p < 0.004). The threefold reduction in stroke may be clinically significant in light of the higher-risk profile of the off-pump group. The limitations of this study are that it was retrospective, there were a small number of events, and different surgeons were involved in the two different approaches to these patients. CONCLUSIONS: Improvements in myocardial protection, revascularization techniques, and anesthetic management have made significant, favorable impacts on CABG outcome in diabetic patients. New diagnostic and therapeutic strategies must be developed to lessen the medical and economic implications of stroke. A larger series or a more effective way of analyzing preoperative risk may well have shown a statistically significant difference in the stroke incidence given the differences in preoperative risk factors/stroke predictors. Until such advances occur, a threefold reduction of stroke incidence using OPCAB certainly makes this technique a favorable one for high-risk diabetics requiring coronary revascularization.

Myocardial revascularization on the beating heart after recent onset of acute myocardial infarction.

OBJECTIVE: Coronary artery bypass grafting (CABG) after the recent onset of acute myocardial infarction (AMI) is associated with high morbidity and mortality. Myocardial revascularization without cardiopulmonary bypass (CPB) has been proposed as an alternative technique to treat these patients in an attempt to decrease the operative risks. METHODS: From January 1995 to June 1999, 518 patients underwent CABG after the recent onset of AMI (1-20 days): 421 patients were revascularized on-CPB and 97 patients off-CPB. Preoperative risk factors (redo operations, congestive heart failure, stroke, extensive calcification of the aorta, and dialysis) were significantly higher in the off-CPB group (p-value < 0.05). Preoperative use of intra-aortic balloon pump (IABP) (off-CPB 5.2% versus on-CPB 2.4%, p-value = NS) and emergent operations (off-CPB 5.2% versus on-CPB 2.6%, p-value = NS) were similar in both groups. Mean number of grafts per patient was 3.46 in the on-CPB group versus 1.82 in the off-CPB group (p-value < 0.005). RESULTS: Actual mortality was 2.9% in the on-CPB group versus 6.2% in the off-CPB group (p-value = NS). Morbidity was comparable in the two groups. Multivariate analysis showed that advanced age, preoperative hemodynamic instability, and left ventricular hypertrophy were independent risk factors for death. Global ischemic time and preoperative hypertension were independently related to postoperative AMI. At univariate and multivariate analysis, CPB was not related to mortality or major postoperative complications. CONCLUSION: Multivariate analysis demonstrates that CABG can be performed safely with or without CPB in patients with recent AMI. CPB is not independently related to mortality or major adverse outcomes.

Robotically assisted video-enhanced-endoscopic coronary artery bypass graft surgery.

Since 1988, through fierce industry-driven competition and patients' preference for minimally invasive procedures, widely diffused through the media, laparoscopic cholecystectomy was universally adopted and rapidly became the "gold standard" for symptomatic cholelithiasis. Robotically assisted video enhanced-endoscopic coronary artery bypass surgery (RAVE-CABG) will most likely follow suit with its similar developmental processes for symptomatic coronary artery disease. Since 1998, there are currently two surgical robotic systems that have been used in a clinical setting for endoscopic coronary artery bypass (ECABG): the da Vinci and the ZEUS system. Although each has separate learning curves to overcome, as with any new technology, both offer the promise to contribute in the interests of reduced hospital days, earlier return to normal activity, less pain, better cosmesis, and the rethinking of surgical dogma such as wide exposure.

On-pump and off-pump coronary artery bypass grafting in the elderly: predictors of adverse outcome.

OBJECTIVE: To establish the role that coronary artery bypass grafting (CABG) without cardiopulmonary bypass (CPB) may have in improving perioperative outcomes of patients 70 years of age and older. BACKGROUND: Coronary revascularization in elderly patients is associated with morbidity and mortality rates higher than those observed in younger patients. The impact of CABG without CPB on perioperative outcomes has not been clearly established. METHODS: This retrospective, nonrandomized study consisted of 1,872 CABG patients. Of these, 1389 underwent CABG with CPB (CPB group) and 483 patients underwent CABG without CPB (off-pump group). Preoperative variables and outcomes were compared between the two groups. Multivariate logistic regression analysis was used to identify independent predictors of mortality, stroke, and adverse outcome. RESULTS: Demographics, Canadian Cardiovascular Society staging, operative priority, and other preoperative variables were comparable between the two groups. The prevalence of previous myocardial infarction was higher in the CPB group (62.6% vs 56.7%; p < 0.005), whereas the prevalence of calcified aorta and preoperative renal failure were higher in the off-pump group (5.4% vs 9.5%; p = 0.04 and 1.7% vs 3.3%; p = 0.04, respectively). Although the graft/patient ratio was higher in the CPB group (3.4 vs 1.9), these patients displayed more extensive coronary artery involvement. At univariate analysis, patients in the off-pump group had a higher rate of freedom from complications (88.2% vs 81.3%; p < 0.005) and a lower incidence of stroke (2.1% vs 4.2%; p = 0.034) than patients in the CPB group. Although there was a trend for a higher actual mortality in the off-pump group (4.8% vs 3.7%; p = ns), the risk adjusted mortality in this group was lower (1.9% vs 2.1%). Multivariate analysis showed that while the use of CPB correlated independently with an increased risk of overall complications, it was not associated with a higher probability of death or stroke. CONCLUSIONS: This investigation suggests that elderly patients undergoing CABG may benefit from off-pump revascularization, as the use of CPB correlated independently with an increased risk of overall complications. However, CPB did not emerge as an independent predictor of death or stroke at multivariate analysis.

OPCAB therapy survey: off-pump clopidogrel, aspirin or both therapy survey.

BACKGROUND: Standards for heparinization during off-pump coronary artery bypass (OPCAB) are lacking. Similarly, there are no established standards for antiplatelet therapy before or after OPCAB. The aim of this study was to determine current practices and standards for both antiplatelet and heparin therapy in OPCAB. METHODS: A postal, multiple-choice survey questionnaire was sent to 800 randomly chosen cardiothoracic surgeons in the United States and Canada. Responses were tabulated and analyzed. RESULTS: The overall response rate was 38% (304 surgeons). The respondents performed CABG in centers with an overall volume between 240 and 1,250 procedures per year (average 380 procedures per year). OPCAB procedures within the same institutions ranged from 20 and 375 cases per year. Sixteen percent (48) of the respondents routinely administer antiplatelet therapy preoperatively; of these, 18% (9) use clopidogrel (Plavix) and 65% (31) aspirin. Eighty-eight percent (267) of the respondents routinely administer antiplatelet therapy after OPCAB. Of these, 24% (65) use clopidogrel and 74% (197) aspirin. Anticoagulation protocols during OPCAB were more variable with 28% (85) administering full dose of heparin, 54% (164) administering half dose heparin, and 13% (40) administering 1/3 dose of heparin during construction of coronary anastomoses. Although 10% (30) maintain an activated clotting time (ACT) above 400 seconds, 70% (213) are content with an ACT above 300 seconds and less than 400 seconds, and 20% (61) responded as "other". The average blood shed postoperatively was 600 ml (range 300 ml and 1 liter). Forty percent (122) administer protamine at half dose, and 60% (182) administer a full dose. CONCLUSION: Although the vast majority of surgeons use antiplatelet therapy postoperatively, a minority administer preoperative antiplatelet agents for OPCAB. The majority of surgeons use a half dose of heparin during OPCAB with ACT maintained above 300 seconds (> 80%). Prospective studies are necessary to determine the short and intermediate effects of antiplatelet therapy and heparinization doses in OPCAB surgery.