Pacing for patients with congestive heart failure and dilated cardiomyopathy

Combination of conditional random field with a rule based method in the extraction of PICO elements

BACKGROUND

Extracting primary care information in terms of Patient/Problem, Intervention, Comparison and Outcome, known as PICO elements, is difficult as the volume of medical information expands and the health semantics is complex to capture it from unstructured information. The combination of the machine learning methods (MLMs) with rule based methods (RBMs) could facilitate and improve the PICO extraction. This paper studies the PICO elements extraction methods. The goal is to combine the MLMs with the RBMs to extract PICO elements in medical papers to facilitate answering clinical questions formulated with the PICO framework.

METHODS

First, we analyze the aspects of the MLM model that influence the quality of the PICO elements extraction. Secondly, we combine the MLM approach with the RBMs in order to improve the PICO elements retrieval process. To conduct our experiments, we use a corpus of 1000 abstracts.

RESULTS

We obtain an F-score of 80% for P element, 64% for the I element and 92% for the O element. Given the nature of the used training corpus where P and I elements represent respectively only 6.5 and 5.8% of total sentences, the results are competitive with previously published ones.

CONCLUSIONS

Our study of the PICO element extraction shows that the task is very challenging. The MLMs tend to have an acceptable precision rate but they have a low recall rate when the corpus is not representative. The RBMs backed up the MLMs to increase the recall rate and consequently the combination of the two methods gave better results.

The patient with a cardiac pacemaker or implanted defibrillator and management during anaesthesia

PURPOSE OF REVIEW

Worldwide, nearly 3 million patients have cardiac pacemakers and more than 300,000 have implantable cardioverter-defibrillators. Many factors cause confusion regarding perioperative care of these patients, since conventional wisdom, case reports, textbooks, and literature reviews have either not kept pace with technologic developments or contain incorrect statements. Additionally, recalls or alert notices have prompted programming changes that might not be understood or recognized.

RECENT FINDINGS

The complexity of the devices, as well as features designed to improve both the quality of life and the survival of the patient, can masquerade as pacing malfunction. Additionally, algorithms designed to detect heart rate, ST segment behavior, and arrhythmias in electrocardiographic monitors may lead to inappropriate behavior on the part of the perioperative team.

SUMMARY

Appropriate education of perioperative practitioners, as well as preoperative interrogation of a pacemaker or implantable cardioverter-defibrillator, may prevent perioperative delays, cancellations, and deaths. Additionally, evidence suggests that postoperative re-interrogation of any cardiac generator is warranted if an operative event includes the use of monopolar electrosurgery ('Bovie') or significant fluid or blood component administration.

Cardiac pacing: the state of the art

Permanent cardiac pacing remains the only effective treatment for chronic, symptomatic bradycardia. In recent years, the role of implantable pacing devices has expanded substantially. At the beginning of the 21st century, exciting developments in technology seem to happen at an exponential rate. Major advances have extended the use of pacing beyond the arrhythmia horizon. Such developments include dual-chamber pacers, rate-response algorithms, improved functionality of implantable cardioverter defibrillators, combinations of sensors for optimum physiological response, and advances in lead placement and extraction. Cardiac pacing is poised to help millions of patients worldwide to live better electrically. We review pacing studies of sick-sinus syndrome, neurocardiogenic syncope, hypertrophic obstructive cardiomyopathy, and cardiac resynchronisation therapy, which are common or controversial indications for cardiac pacing. We also look at the benefits and complications of implantation in specific arrhythmias, suitability of different pacing modes, and the role of permanent pacing in the management of patients with heart failure.

Resynchronization therapy for the management of heart failure

Biventricular pacing offers real benefit to some patients with HF, but several questions remain unanswered. One is which patients will benefit the most from this technology. Although there are some indications, the ideal patient group has yet to be identified. The best electrical configuration for pacing and the best pacing site have not been identified for all patients. Another question is whether resynchronization will improve mortality rates. A final question is the cost-effectiveness of this therapy. Studies in progress may answer some of these questions. Meanwhile, this intervention offers hope for improved quality of life and perhaps survival in this high-risk patient population.

Management of heart failure: use of biventricular pacing

Congestive heart failure (CHF) is a clinical syndrome that affects more than 4 million people in the United States. The grim prognosis for this population has led to a search for new therapies to treat CHF. Resynchronization of the ventricles is one such therapy. The pathophysiology associated with conduction defects and the evolution of the use of pacing technologies for this patient population will be discussed. Early data have been encouraging, suggesting that patients may gain important hemodynamic, functional, and quality-of-life improvements with biventricular pacing.

Prevalence of potential candidates for biventricular pacing among patients with known coronary artery disease: a prospective registry from a single center

New forms of ventricular pacing are increasingly studied as an option in the management of patients with heart failure. Coronary artery disease (CAD) is the most frequent cause of heart failure, and patients with complete left or right bundle branch block (LBBB and RBBB) and a reduced left ventricular ejection fraction (LVEF) are the best candidates for this new therapy. However, the prevalence of this clinical presentation is uncertain. During a 1-year period, 433 patients with documented CAD (mean age 64 +/- 10 years, 79% men) who were referred for myocardial perfusion imaging were prospectively studied. All patients underwent a 2-day stress-rest gated 99mTc-Tetrofosmin SPECT study with evaluation of resting LV enddiastolic (LVEDV) and endsystolic (LVESV) volumes and LVEF. The resting ECG was examined in all patients for the presence of complete LBBB or RBBB. Of the 433 patients with CAD 36 patients (8.3%) had LBBB (n = 14) or RBBB (n = 22) and a QRS width > 120 ms. These 36 patients were in general older and more frequently had diabetes and atrial fibrillation. Patients with LBBB or RBBB had a significantly lower LVEF (41 +/- 16% vs 48 +/- 14%, P < 0.01) and significantly higher LV volumes compared to patients without LBBB or RBBB (177 +/- 79 mL vs 131 +/- 53 mL, P < 0.001 for LVEDV and 116 +/- 76 mL vs 73 +/- 49 mL, P < 0.001 for LVESV). In total, 112/433 (26%) had an LVEF < or = 40%; 16 had also a LBBB or RBBB (3.7% of the whole population, 14% of the patients with a LVEF < or = 40%). Within the group of patients with a LVEF > or = 40%, patients with BBB had comparable LVEF (26 +/- 9% vs 30 +/- 8%, P = NS) but significantly higher LVEDV and LVESV (230 +/- 70 mL vs 190 +/- 64 mL, P < 0.05 for LVEDV and 170 +/- 65 mL vs 135 +/- 56 mL, P < 0.05 for LVESV). In this prospective registry 3.7% of all patients with known CAD had LBBB or RBBB in combination with a LVEF < or = 40%. This represented 14% of all patients with a LVEF > or = 40%. These limited numbers should be kept in mind when considering biventricular pacing as a new therapeutic options in patients with heart failure.