Akira Nozaki

Onset of induced atrial flutter in the canine pericarditis model.

To test the hypothesis that induced atrial flutter evolves from a transitional rhythm, the onset of 99 episodes of induced atrial flutter (mean cycle length 135 +/- 18 ms) lasting greater than 5 min in 40 dogs with sterile pericarditis was first characterized. In 85 (86%) of the 99 episodes, atrial flutter was preceded by a brief period (mean 1.4 +/- 0.9 s, range 0.4 to 42) of atrial fibrillation. Then, in 11 open chest studies, atrial electrograms were recorded simultaneously from 95 pairs of right atrial electrodes during the onset of 18 episodes of induced atrial flutter (mean cycle length 136 +/- 16 ms). Atrial flutter was induced by a train of eight paced atrial beats, followed by one or two premature atrial beats (7 episodes) or rapid atrial pacing (11 episodes). A short period of atrial fibrillation (mean cycle length 110 +/- 7 ms) induced by atrial pacing activated the right atrium through wave fronts, which produced a localized area of slow conduction. Then unidirectional conduction block of the wave front occurred for one beat in all or a portion of the area of slow conduction. This permitted the unblocked wave front to turn around an area of functional block and return through the area of slow conduction that had developed the unidirectional conduction block, thereby initiating the reentrant circuit. The location of the unidirectional block relative to the direction of the circulating wave fronts determined whether the circus movement was clockwise or counterclockwise. The area of slow conduction and unidirectional conduction block occurred where the wave front crossed perpendicular to the orientation of the atrial muscle fibers, suggesting a role for anisotropic conduction. These areas included the high right atrial portion of the sulcus terminalis (10 episodes), the low right atrial portion of the sulcus terminalis (4 episodes) and the pectinate muscle region (4 episodes). It is concluded that the development of a localized area of slow conduction in the right atrium followed by unidirectional conduction block in this area produced during a short period of atrial fibrillation or rapid atrial pacing is necessary for atrial flutter to occur in this model.

Characterization of double potentials in a functionally determined reentrant circuit. Multiplexing studies during interruption of atrial flutter in the canine pericarditis model.

OBJECTIVES We tested the hypothesis that double potentials recorded during atrial flutter in a functionally determined reentrant circuit reflect activation of the reentrant wave front around an area of functional conduction block. BACKGROUND The center of the atrial flutter reentrant circuit in the sterile pericarditis canine model is characterized by double potentials. METHODS We studied 11 episodes of atrial flutter in eight dogs during interruption of atrial flutter while pacing the atria. A multielectrode mapping system was used to record simultaneously from 190 electrodes on the right atrium (location of reentry). RESULTS Interruption of atrial flutter occurred when the orthodromic wave front from the pacing impulse blocked in an area of slow conduction in the reentrant circuit. The response of the double potential with interruption of atrial flutter depended on the location of the recording site relative to this area of block. Two types of response were seen. When the double potential was recorded orthodromically distal to this area of block, interruption of atrial flutter was associated with disappearance of the second deflection, and continued pacing after interruption of atrial flutter was not associated with reappearance of the second potential. When the double potential was recorded at a site orthodromically proximal to the area of block, interruption of atrial flutter was not associated with disappearance of the second potential, and when rapid atrial pacing was continued, the double potential remained despite disappearance of the atrial flutter reentrant circuit. CONCLUSIONS Double potentials represent functional conduction block in the center of the reentrant circuit, with each deflection of the double potential reflecting activation on either side of the area of functional block. The data also demonstrate that double potentials are not limited to a reentrant circuit, as they were recorded on either side of an area of block in the absence of such a circuit.

Multiplexing studies of effects of rapid atrial pacing on the area of slow conduction during atrial flutter in canine pericarditis model.

BackgroundWe report that rapid atrial pacing interrupts atrial flutter when the orthodromic wave front from the pacing impulse is blocked in an area of slow conduction in the reentry circuit. To characterize the area of slow conduction during atrial flutter and rapid pacing, we studied 11 episodes of induced atrial flutter, mean cycle length 157 ± 20 msec, in eight dogs with sterile pericarditis. Methods and ResultsAtrial electrograms were recorded simultaneously from 95 pairs of right atrial electrodes during the interruption of atrial flutter by rapid atrial pacing, mean cycle length 139 ± 21 msec. Areas of slow conduction during atrial flutter were demonstrated at one to three sites in the reentry circuit. After rapid pacing captured the reentry circuit, one area of slow conduction either disappeared (10 episodes) or the degree of slow conduction in an area of slow conduction decreased (one episode). Both changes were in association with activation of the region by a wave front from the pacing impulse that arrived from a direction different than that during the induced atrial flutter. Interruption of atrial flutter during rapid pacing occurred when the orthodromic wave front from the pacing impulse blocked in an area of slow conduction that had either newly evolved during rapid pacing (seven episodes) or that was previously present (four episodes). ConclusionsAreas of slow conduction present during atrial flutter and rapid pacing of atrial flutter are functional and depend on both the atrial rate and the direction of the circulating wave fronts. Interruption of atrial flutter by rapid pacing results from block of the orthodromic wave front of the pacing impulse in an area of slow conduction in the reentry circuit. (Circulation 1991;83:983–994)

Mechanism of interruption of atrial flutter by moricizine. Electrophysiological and multiplexing studies in the canine sterile pericarditis model of atrial flutter.

BACKGROUND Moricizine is said to have potent effects on cardiac conduction but little or no effect on cardiac refractoriness. METHODS AND RESULTS The effects of moricizine (2 mg/kg IV) on induced atrial flutter were studied 2 to 4 days after the creation of sterile pericarditis in 11 dogs. Ten episodes of stable atrial flutter before and after the administration of moricizine were studied in 9 dogs in the conscious, nonsedated state, and 7 episodes were studied in 6 dogs in the anesthetized, open chest state. In the conscious state, the effects of moricizine on atrial excitability, atrial effective refractory period, and intra-atrial conduction times were studied by recording during overdrive pacing of sinus rhythm from epicardial electrodes placed at selected atrial sites. Moricizine prolonged the atrial flutter cycle length in all the episodes, from a mean of 133 +/- 9 to 172 +/- 27 milliseconds (P < .001), and then terminated 7 of the 10 episodes. Moricizine increased the atrial threshold of excitability from a mean of 2.3 +/- 1.4 to 3.3 +/- 2.2 mA (P < .01) and prolonged intra-atrial conduction times (measured from the sulcus terminalis to the posteroinferior left atrium) from a mean of 58 +/- 6 to 64 +/- 5 milliseconds (P < .005). Prolongation of the atrial effective refractory period from 166 +/- 20 to 174 +/- 24 milliseconds (P < .05) was observed only at the sulcus terminalis site. In the open chest studies, administration of moricizine prolonged the atrial flutter cycle length from a mean of 150 +/- 15 to 216 +/- 30 milliseconds (P < .001) and then terminated the atrial flutter in all 7 episodes. As demonstrated by simultaneous multisite mapping from 95 bipolar sites on the right atrial free wall, the atrial flutter cycle length prolongation was either due to further slowing of conduction in an area of slow conduction in the reentrant circuit of the atrial flutter (5 episodes) or further slowing of conduction in an area of slow conduction plus the development of a second area of slow conduction (2 episodes). The change in conduction times in the rest of the reentrant circuit was negligible (10.9 +/- 8.7% of the total change). In all 7 episodes, the last circulating reentrant wave front blocked in an area of slow conduction. CONCLUSIONS Moricizine (1) prolongs the atrial flutter cycle length, primarily by slowing conduction in an area of slow conduction in the reentrant circuit, (2) terminates atrial flutter by causing block of the circulating reentrant wave front in an area of slow conduction of the reentrant circuit, and (3) effectively interrupts otherwise stable atrial flutter in this canine model. The reason for these effects of moricizine are not readily explained by its effects on global atrial conduction times and refractoriness studied during sinus rhythm. Local changes in conduction in an area(s) of slow conduction are responsible for both cycle length prolongation and atrial flutter termination rather than the traditional wavelength concept of head-tail interaction.

Silent Double Aortic Arch Found in an Elderly Man

A 73-year-old male was hospitalized for cerebral bleeding in his thalamus and complained of chest pain during his hospitalization. During the heart attack, the ECG showed an ST-segment depression in leads II, III, and aVF. A thulium cardiac scintigram showed an inferior redistribution, indicating the presence of coronary heart disease. The patient had a history of hypertension and hypercholesterolemia, but no history of bronchial asthma or esophageal problems. Three months later, the patient was transferred to the cardiology department and a cardiac catheterization was scheduled. A plain chest roentgenogram showed a bilateral …

Observational study of the effects of dabigatran on gastrointestinal symptoms in patients with non-valvular atrial fibrillation

Dyspepsia (including upper abdominal pain, abdominal pain, abdominal discomfort, epigastric discomfort, and dyspepsia) is a symptom that is carefully monitored during dabigatran treatment. However, detailed information on dyspepsia, including onset, duration, severity, and use of drug treatment, has not yet been established in Japanese patients.

Pulmonary Embolism Due to Popliteal Venous Aneurysm

A 33-year-old man was admitted to our hospital for shortness of breath on exertion. His symptoms started suddenly a week before admission when he was driving a car and worsened daily. He was amateur football player and had no history of hypertension, dyslipidemia, diabetes mellitus, smoking, or leg injury. On admission, an arterial pulse oxygen saturation monitor showed that his arterial blood oxygen saturation was 94% with room air. His blood pressure was 114/82 mm Hg and his pulse rate was 92/min with regular rhythm. His height was 162 cm and body weight was 62 kg. No other outstanding physical abnormalities were observed. Laboratory data showed slightly an elevated C-reactive protein level of 0.87 mg/dL with a normal white blood cell count of 6100 cells/mL. Arterial blood sampling revealed a normal CO2 level of 41 mm Hg and pH of 7.42 with low oxygen tension (52 mm Hg). An ECG showed a small S wave in lead I and a small Q wave and inverted T wave in …