Newly developed signal-averaged vector-projected 187-channel electrocardiogram can evaluate the spatial distribution of repolarization heterogeneity

The purpose of this study was to verify the spatial distribution of myocardial repolarization heterogeneity using a newly developed 187-channel signal-averaged vector-projected ECG (187-ch SAVP-ECG). We constructed corrected recovery time (RTc) and Tpeak-end (corrected Tp-e) dispersion maps using a 187-ch SAVP-ECG based on vector-projection theory using a Mason-Likar lead system. We compared the spatial distribution and quantitative values of dispersion maps by 187-ch SAVP-ECG with those by 64-ch magnetocardiography (MCG) in 27 normal controls (control) and 16 patients (12 myocardial infarction (MI), and 4 dilated cardiomyopathy (DCM)). The wave pattern of the 187-ch SAVP-ECG in the representative cases was similar to those in 64-ch MCG. Spatial distribution increased RTc and corrected Tp-e dispersion maps defined by 187-ch SAVP-ECG were in agreement with those by 64-ch MCG. The value of RTc dispersion in MI was higher than that in control (41 +/- 21 ms in MI versus 30 +/- 12 ms in control, P < 0.05). The value of corrected Tp-e dispersion in DCM was higher than that in control (58 +/- 12 ms in DCM versus 30 +/- 13 ms in control, P < 0.001). There was a good correlation between RTc and corrected Tp-e dispersion values determined by 187-ch SAVP-ECG and 64-ch MCG modalities (y = 0.46x + 18, r = 0.62, P = 0.02 for RTc dispersion; y = 0.52x + 15, r = 0.63, P = 0.01 for corrected Tp-e dispersion). RTc and corrected Tp-e dispersion maps by 187-ch SAVP-ECG based on vector-projection theory can evaluate the spatial distribution of myocardial repolarization heterogeneity.     

Allergic bronchial asthma: airway inflammation and hyperresponsiveness

The international consensus report on diagnosis and treatment of asthma was published in 1992 (Clin Exp Allergy 22: 1-72). According to the report, asthma is a chronic inflammatory disorder of the airways in which many cells play a role, including mast cells and eosinophils. Airway inflammation causes various symptoms of asthma which are usually associated with widespread but variable airflow obstruction and causes an associated increase in airway responsiveness to a variety of stimuli. The definition of asthma, provided in this report, is an epoch-making revision of the conventional recognition of asthma based on respiratory physiology and does not contradict the empirical knowledge that asthma responds well to steroid therapy. One reason, which led airway inflammation to be understood as a major factor in the pathophysiology of asthma is the technological advance and the widespread use of bronchoscopes. The use of bronchoscopy as a research tool has markedly improved the understanding of the pathology of asthma. It became also possible to link biopsy findings to autopsy findings in patients who died of asthma. However, it is relatively difficult to repeat a biopsy of the airway mucosal membranes in individual asthmatic patients. Here, animal models of asthma play a significant role. Findings from animal models can provide a clue for the development of new anti-asthmatic drugs. This paper will deal with the paradigm of allergic asthma and focus on recent topics of interleukin (IL)-4 and IL-5, which seem to play a central role in allergic asthma. The causative relationship between airway inflammation and hyperresponsiveness will be discussed.     

A case of Wolff-Parkinson-White syndrome: conduction through the Kent bundle seems to depend on the serum potassium level

A 72-year-old man with Wolff-Parkinson-White syndrome and sick sinus syndrome had colon cancer, suggesting that the conduction of the Kent bundle depends on the serum potassium level. Because of severe diarrhea or furosemide administration, the serum potassium level in this patient was sometimes low. When it was less than 3.0 mEq/l delta wave or re-entrant tachycardia via the Kent bundle occurred. These were suppressed by the administration of potassium. On the other hand, when the serum potassium level was normal or high, neither effect was noted, and electrophysiological studies, done when the level was 3.2 mEq/l, showed no evidence of conduction by the accessory pathway. This suggests that conduction through the Kent bundle depends on the serum potassium level.     

Effects of heart rate on coronary circulation and external mechanical efficiency in elderly hypertensive patients with left ventricular hypertrophy

Background and hypothesis: Mechanisms of heart failure in elderly hypertensive patients with hypertrophy have not been studied sufficiently. We hypothesized that impaired increment of coronary blood flow in response to increases in heart rate could be responsible for the occurrence or aggravation of heart failure. Methods: To test this hypothesis, we measured coronary hemodynamics and lactate balance during basal conditions and atrial pacing in 21 elderly patients aged ≥ 65 years (mean 74 ± 6 years) without coronary arterial disease: 7 normoten-sive control patients (Group 1), 7 hypertensive hypertrophic patients without a history of congestive heart failure (Group 2), and 7 patients with such history (Group 3). Coronary sinus blood flow (CSBF) was measured in coronary sinus using a thermodilution catheter. Results: During basal conditions, heart rate did not differ among the three groups (67 ± 3 in Group 1,65 ±11 in Group 2, and 63 ± 6 beats/min in Group 3). CSBF was significantly higher in the two hypertrophic groups than in the control group, but CSBF normalized by left ventricular mass was significantly lower in both hypertrophic groups. External mechanical efficiency (EME) obtained as left ventricular work divided by myocardial oxygen consumption did not differ among groups during basal conditions (36 ± 9% in Group 1, 35 ± 8% in Group 2, and 29 ± 9% in Group 3, NS). During atrial pacing to increase heart rate by 25 ± 5% (lower) and 54 ± 6% (higher), the increases in CSBF were markedly limited in both hypertrophic groups, and the response in Group 3 was more depressed than that in Group 2. EME did not change in the control group or in Group 2, but did decrease to 21 ± 5% in Group 3 during the higher pacing rate (p <0.01 vs. basal conditions). in this group, the relationship between EME and heart rate showed a significant negative correlation (r = —0.56, p = 0.02). Lactate balance in coronary sinus blood showed a tendency to production in Group 3 during the higher pacing rate, suggesting myocardial ischemia. Conclusion: These findings suggest that in hypertensive hypertrophic patients with a history of heart failure, the coronary circulation system is vulnerable to increasing heart rate. in medical treatment of elderly hypertensive patients, control of heart rate in addition to blood pressure control should be considered to minimize the occurrence or aggravation of heart failure.