High-resolution electrical mapping of porcine gastric slow-wave propagation from the mucosal surface.

BACKGROUND: Gastric motility is coordinated by bioelectrical slow waves, and gastric dysrhythmias are reported in motility disorders. High-resolution (HR) mapping has advanced the accurate assessment of gastric dysrhythmias, offering promise as a diagnostic technique. However, HR mapping has been restricted to invasive surgical serosal access. This study investigates the feasibility of HR mapping from the gastric mucosal surface. METHODS: Experiments were conducted in vivo in 14 weaner pigs. Reference serosal recordings were performed with flexible-printed-circuit (FPC) arrays (128-192 electrodes). Mucosal recordings were performed by two methods: (i) FPC array aligned directly opposite the serosal array, and (ii) cardiac mapping catheter modified for gastric mucosal recordings. Slow-wave propagation and morphology characteristics were quantified and compared between simultaneous serosal and mucosal recordings. KEY RESULTS: Slow-wave activity was consistently recorded from the mucosal surface from both electrode arrays. Mucosally recorded slow-wave propagation was consistent with reference serosal activation pattern, frequency (P≥.3), and velocity (P≥.4). However, mucosally recorded slow-wave morphology exhibited reduced amplitude (65-72% reduced, P<.001) and wider downstroke width (18-31% wider, P≤.02), compared to serosal data. Dysrhythmias were successfully mapped and classified from the mucosal surface, accorded with serosal data, and were consistent with known dysrhythmic mechanisms in the porcine model. CONCLUSIONS & INFERENCES: High-resolution gastric electrical mapping was achieved from the mucosal surface, and demonstrated consistent propagation characteristics with serosal data. However, mucosal signal morphology was attenuated, demonstrating necessity for optimized electrode designs and analytical algorithms. This study demonstrates feasibility of endoscopic HR mapping, providing a foundation for advancement of minimally invasive spatiotemporal gastric mapping as a clinical and scientific tool.

Rapid high-amplitude circumferential slow wave propagation during normal gastric pacemaking and dysrhythmias.

BACKGROUND: Gastric slow waves propagate aborally as rings of excitation. Circumferential propagation does not normally occur, except at the pacemaker region. We hypothesized that (i) the unexplained high-velocity, high-amplitude activity associated with the pacemaker region is a consequence of circumferential propagation; (ii) rapid, high-amplitude circumferential propagation emerges during gastric dysrhythmias; (iii) the driving network conductance might switch between interstitial cells of Cajal myenteric plexus (ICC-MP) and circular interstitial cells of Cajal intramuscular (ICC-IM) during circumferential propagation; and (iv) extracellular amplitudes and velocities are correlated. METHODS: An experimental-theoretical study was performed. High-resolution gastric mapping was performed in pigs during normal activation, pacing, and dysrhythmia. Activation profiles, velocities, and amplitudes were quantified. ICC pathways were theoretically evaluated in a bidomain model. Extracellular potentials were modeled as a function of membrane potentials. KEY RESULTS: High-velocity, high-amplitude activation was only recorded in the pacemaker region when circumferential conduction occurred. Circumferential propagation accompanied dysrhythmia in 8/8 experiments was faster than longitudinal propagation (8.9 vs 6.9 mm s(-1) ; P = 0.004) and of higher amplitude (739 vs 528 µV; P = 0.007). Simulations predicted that ICC-MP could be the driving network during longitudinal propagation, whereas during ectopic pacemaking, ICC-IM could outpace and activate ICC-MP in the circumferential axis. Experimental and modeling data demonstrated a linear relationship between velocities and amplitudes (P < 0.001). CONCLUSIONS & INFERENCES: The high-velocity and high-amplitude profile of the normal pacemaker region is due to localized circumferential propagation. Rapid circumferential propagation also emerges during a range of gastric dysrhythmias, elevating extracellular amplitudes and organizing transverse wavefronts. One possible explanation for these findings is bidirectional coupling between ICC-MP and circular ICC-IM networks.

Radiofrequency treatment of hepatic neoplasms in patients with permanent pacemakers.

Clinicians who provide care for patients with implantable devices for rhythm management, ie, pacemakers and internal cardioverter defibrillators, must be aware of sources of interference that could affect device function. Intracardiac radiofrequency is a recognized source of potential interference. However, radiofrequency to extracardiac sites that are relatively close to the implanted device has not been investigated thoroughly. We present 2 patients with permanent pacemakers undergoing intrahepatic radiofrequency for the treatment of metastatic disease. No interference was documented in either patient. Additional in vitro and in vivo studies are needed to determine definite clinical guidelines for such patients.

Characteristics of presenting electrocardiograms of acute myocardial infarction from a community-based population predict short- and long-term mortality.

To investigate the relevance of presenting electrocardiographic (ECG) patterns to short- and long-term mortality in nonreferral patients with acute myocardial infarction (AMI), 6 ECG patterns were analyzed. A consecutive series of 907 patients from Olmsted County, Minnesota, admitted to the Mayo Clinic Cardiac Care Unit from January 1, 1988 to March 31, 1998 for acute myocardial infarction comprised the study population. ECG patterns and distribution in the population were: (1) ST elevation alone (20.8%), (2) ST elevation with ST depression (35.2%), (3) normal or nondiagnostic electrocardiograms (18.5%), (4) ST depression alone (11.8%), (5) T-wave inversion only (10.7%), and (6) new left bundle branch block (LBBB) (3.0%). Seven- and 28-day mortalities varied significantly (p <0.01) among the 6 ECG groups. Respective mortalities were 3.0% and 6.0% for patients with normal or nondiagnostic electrocardiograms, 3.1% and 5.2% for T-wave inversion only, 7.4% and 10.6% for ST elevation alone, 9.4% and 13.1% for ST depression alone, 10.3% and 13.8% for ST elevation with ST depression, and 18.5% and 22.2% for new LBBB. Length of hospital stay (LOS) also varied among the ECG pattern groups (p <0.001) with the longest average LOS being in the new LBBB group (12.5 days). Long-term survival was similar among 5 ECG pattern groups (45% to 55% at 8 years from discharge) with the exception of LBBB (20% at 8 years). Among non-LBBB groups, ST-segment depression with or without ST elevation was associated with increased short-term mortality. Also, in this community-based population, 18.5% of patients had normal or nondiagnostic electrocardiograms.

Aortic valve involvement in calciphylaxis: uremic small artery disease with medial calcification and intimal hyperplasia.

Calciphylaxis is a rare manifestation of abnormal calcium metabolism seen in some patients with renal disease. We describe the transesophageal echocardiographic (TEE) findings in a patient with calciphylaxis. These findings included calcification of ascending aorta and aortic valve. TEE was normal before the development of calciphylaxis.

Choosing the most appropriate treatment for stable angina. Safety considerations.

The goals of stable angina pectoris treatment are: (i) symptom relief and increase in angina-free walking time; and (ii) reduction of mortality and adverse outcome. Strategies used for plaque stabilisation resulting in a reduction in cardiovascular mortality and morbidity are: smoking cessation; aspirin (acetylsalicylic acid); blood pressure control; lipid lowering agents when low density lipoprotein cholesterol is elevated despite dietary therapy; coronary bypass surgery in patients with left main stem disease or triple vessel coronary disease and diminished left ventricular function; and use of estrogen in postmenopausal women. For symptom relief and to increase angina-free walking time, long acting nitrates, beta-blockers, calcium antagonists and potassium channel openers can be used. Drugs from these 3 classes are all effective when used optimally and choice of initial therapy should consider the presence of concomitant disease and underlying left ventricular function. However, none of the long acting nitrates provide continuous prophylaxis because nitrate tolerance develops during long term therapy. In patients with uncomplicated stable angina, nitrates, beta-blockers and calcium antagonists are all effective. Intermittent nitrate therapy is not associated with tolerance, but headache is a common adverse effect and the patient is unprotected at night and in the early hours of the morning. Concomitant treatment with a beta-blocker may be beneficial if the patient experiences withdrawal or early morning angina. For patients with stable angina and hypertension, therapy with a beta-blocker or a calcium antagonist rather than nitrate is indicated. beta-Blockers are preferred in patients who have had a myocardial infarction, or in those with a history of supraventricular tachyarrhythmias. beta-Blockers may produce excessive slowing of the heart rate, fatigue and bronchospasm in susceptible patients. Calcium antagonists are indicated as initial therapy when beta-blockers are either not tolerated or contraindicated. beta-Blockers and nondihydropyridine calcium antagonists should not be used in patients with sinus bradycardia and those with greater than first degree atrioventricular (AV) block because of the possibility of further slowing of heart rate and/or the development of high grade AV block. When monotherapy with one class is ineffective or associated with adverse effects, the patient should be switched to another class rather than given an additional drug. Optimal monotherapy is often as effective as combination therapy. If maximum monotherapy is only partially effective, a combination therapy which is not additive in terms of adverse effects should be chosen. Triple therapy may be deleterious and no more effective than dual therapy.

Successful management of myocardial infarction during pregnancy in a renal transplant recipient.

Myocardial infarction (MI) complicating pregnancy in a renal transplant recipient is described. Management challenges of MI in pregnancy and the possible predisposing roles of renal transplantation and erythropoietin (EPO) use are discussed.

Large pulmonary vein varix diagnosed by transesophageal echocardiography: an unusual site for thrombus in atrial fibrillation.

An elderly man with pulmonary vein varix and atrial fibrillation is described. The diagnosis of pulmonary varix, a localized dilatation of pulmonary vein, was made by transesophageal echocardiography. The patient had chronic atrial fibrillation, and transesophageal echocardiography demonstrated thrombus in the pulmonary varix. In patients with atrial fibrillation, pulmonary varix may be an unusual site for thrombus formation.

Severe symptomatic sinus bradycardia associated with mesalamine use.

A 29-yr-old white woman was hospitalized with bloody diarrhea secondary to ulcerative colitis. Within 24 h of receiving intravenous steroids, loperamide, and mesalamine, she developed symptomatic hypotension, severe sinus bradycardia, sinus pauses, and junctional escape beats. The hypotension and sinus bradycardia resolved after discontinuing mesalamine. She had a family history of conduction tissue disease but her exercise ECG and Holter studies were normal. She was rehospitalized 6 wk later with an exacerbation of ulcerative colitis and, within 8 h of receiving mesalamine, developed hypotension and severe sinus bradycardia, which resolved after stopping mesalamine. Thus mesalamine should be used with caution, especially in patients predisposed to cardiac conduction tissue disease.

Unusual presentation of late regional cardiac tamponade after aortic surgery.

Localized pericardial effusion leading to cardiac tamponade is seen occasionally in patients after cardiac surgery. This condition may be difficult to diagnose clinically because of unusual presenting symptoms and absence of conventional signs of cardiac tamponade. A case of localized pericardial effusion with presenting symptoms of fever and increasing fatigue is described in this study. The definitive diagnosis was made using transesophageal echocardiography. Surgical drainage of localized effusion resulted in prompt hemodynamic and symptomatic improvement.