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Biomedical subjects

D Wu

Publications and source records attributed to D Wu.

At least 613 records · Page 34Linked to original sources
PubMed1980

Membrane deenergization by colicin K affects fluorescence of exogenously added but not biosynthetically esterified parinaric acid probes in Escherichia coli.

Fluorescence of the conjugated polyene fatty acid, parinaric acid (PnA), was studied in membranes of Escherichia coli during deenergization by colicin K. The free fatty acid and biosynthetically esterified forms of cis-PnA (9,11,13,15-cis,trans,trans,cis-octadecatetraenoic acid), both of which are sensitive to E. coli lipid-phase transitions, were compared. When free cis-PnA was added exogenously to respiring bacteria, dissipation of the energized state of the membrane resulted in a dramatic increase in cis-PnA fluorescence; all-trans-PnA was much less sensitive. Neither spectral shifts nor a change in cis-PnA fluorescence polarization were observed. Analysis of the PnA content of extracellular fractions of deenergized and control cells revealed a difference in probe distribution: the membranes of energy-poisoned E. coli bound about 77% of exogenously added cis-PnA, whereas membranes of actively respiring controls bound only about 44%. No fluorescence enhancement was observed in cells centrifuged to remove unbound cis-PnA before colicin treatment. When cis-PnA was biosynthetically esterified to phospholipids of an unsaturated fatty acid auxotroph of E. coli, the fluorescence did not change during membrane deenergization. In double-probe experiments, membrane deenergization resulted in fluorescence enhancement of exogenously added N-phenyl-1-naphthylamine, without change in esterified PnA fluorescence. We conclude that deenergization of E. coli membranes leads to increased binding and fluorescence of exogenously added PnA and cannot be detected from within the inner and outer membranes by PnA esterified in vivo.

Cell Membrane↗
PubMed1980

Chronic longterm electrophysiologic study of paroxysmal ventricular tachycardia.

Nine patients with recurrent paroxysmal ventricular tachycardia underwent chronic electrophysiologic studies to delineate effective drug therapy for prevention of recurrence of this arrhythmia. The frequency of attacks of ventricular tachycardia necessitating hospitalization ranged from 2 to 12 (mean 5 +/- 4) attacks per year. Pacing induction of ventricular tachycardia was performed prior to and following intravenous or oral administration of procainamide (eight patients), disopyramide phosphate (nine patients), aprindine (five patients) and propranolol (four patients). Successful drug response (prevention of ventricular tachycardia induction or induction of nonsustained episodes of tachycardia) was noted in six of nine patients (66 percent). Lack of drug effect on the ability to sustain ventricular tachycardia was noted in three patients (34 percent). In addition, a deleterious drug response, manifested by potentiation of ventricular flutter or fibrillation, was observed in two of the three patients who failed to respond to drugs. Chronic drug therapy based on successful response in six patients resulted in cure of ventricular tachycardia in five of six patients (83 percent), one patient having one attack necessitating hospitalization. Of the three patients who demonstrated lack of drug effect during chronic electrophysiologic studies, one died suddenly and two had recurrent episodes of ventricular tachycardia while receiving a drug that did not prevent induction of ventricular tachycardia.

Adult↗
PubMed1979

Incidence and site of atrioventricular block in patients with chronic bifascicular block.

Four hundred fifty-two patients with chronic bifascicular block and initially intact atrioventricular (AV) conduction were detected, studied, and prospectively followed between January 1970 and March 1978. There were 360 males and 92 females, ages 18--93 years (mean +/- SD, 62 +/- 15 years). Follow-up ranged from 29-2804 days (mean 1066 +/- 97 days). AV block (2 degrees or 3 degrees) developed in 29 patients, nine with apparent cause and spontaneously in 20. Cumulative annual incidence of all heart block for 1--5 years was, respectively, 4%, 5.9%, 8.7%, 10.1% and 11.3%, and for spontaneous block was 2%, 3.1%, 5.2%, 6.7%, and 7.1%. Sites of spontaneous block were probably or definitely AV nodal in ten, His bundle in one, and trifascicular in nine. Cumulative incidence of AV block in surviving bifascicular block patients is 11% at 5 years, with 7% reflecting spontaneous block. The probable or definite site of AV block varies and is trifascicular in less than half of the patients. The small incidence of trifascicular block probably explains the difficulty in predicting this complication with electrophysiological studies.

Adolescent↗
PubMed1979

Congenital abnormalities of the conduction system in two patients with tachyarrhythmias.

Serial sections of the conduction system (CS) were performed in two patients with recurrent tachyarrhythmias. Case 1, a 34-year-old female who had dual atrioventricular (AV) nodal pathways with recurrent paroxysmal supraventricular tachycardia, committed suicide. Autopsy revealed an abnormally formed atrial septum with insertion of eustachian valve on the AV part of the pars membranacea. The intercuspid portion of the pars membranacea was muscular. The AV node was located adjacent to the membranous part of the ventricular septum rather than the central fibrous body. In addition, there was an accessory anterior AV node on the parietal wall of the right atrium. Case 2, a 13-year-old boy with history of recurrent ventricular tachycardia, died suddenly. CS revealed a right-sided, markedly septated bundle. The first part of right bundle branch was divided into three parts, which later joined together. Both cases showed fatty infiltration of the atrial septum, more than normal for the age of the patients. The relationship of the recurrent tachyarrhythmias to the congenital abnormalities in the CS in the two cases and the fatty infiltration is reviewed.

Adolescent↗
PubMed1979

Effects of atropine on induction and maintenance of atrioventricular nodal reentrant tachycardia.

The electrophysiologic effects of atropine were studied in 14 patients with dual atrioventricular (AV) nodal pathways and recurrent paroxysmal supraventricular tachycardia (PSVT). During PSVT, all patients used a slow pathway (SP) for antegrade and fast pathway (FP) for retrograde conduction. Atropine enhanced both SP antegrade and FP retrograde conduction, shown by a decrease in paced cycle lengths (atrial and ventricular) producing AV and ventriculoatrial block. Five patients had induction of sustained PSVT before and after atropine. Seven patients failed to induce or sustain PSVT before atropine, because of retrograde FP refractoriness. All seven had induction of sustained PSVT after atropine due to facilitation of FP retrograde conduction. Two patients had only single atrial echoes before atropine, reflecting SP antegrade refractoriness. After atropine, sustained PSVT was inducible in one, and nonsustained in the other, PSVT cycle length could be compared in seven patients before and after atropine and decreased from 383 +/- 25 to 336 +/- 17 (p less than 0.05). Thus, in patients with dual AV nodal pathways, atropine facilitated SP antegrade and FP retrograde conduction, shortened cycle length of PSVT and potentiated ability to sustain PSVT.

Adult↗
PubMed1979

Significance of chronic bifascicular block without apparent organic heart disease.

Eighty-six of 452 patients (19%) with chronic bifascicular block were found to have no clinically apparent associated organic heart disease (OHD) and were defined as having primary conduction disease (PCD). Comparison of patients with PCD and OHD revealed a significantly lower incidence of the following clinical variables in the PCD patients (p less than 0.001): exertional angina, dyspnea, congestive heart failure, cardiomegaly, functional class I (all by study design), left bundle branch block and premature ventricular contractions. Both mean AH and HV intervals were significantly shorter in patients with PCD (p less than 0.01). The incidence of HV prolongation was 21% in PCD and 41% in OHD patients (p less than 0.001). All patients were prospectively followed for 21-2998 days with a mean +/- SEM of 1209 +/- 66 days for PCD and 1172 +/- 36 days for OHD. Atrioventricular (AV) block developed in three patients from the PCD group and 26 from the OHD group (NS), with spontaneous block occurring in one (1%) PCD patient and 19 (5%) OHD patients (p less than 0.05). Annual mortality due to sudden death as well as total cardiovascular mortality (including sudden death) for the 5-year follow-up was significantly lower in patients with PCD. Patients with PCD have significantly lower incidence of electrophysiologic abnormalities and subsequent spontaneous AV block as well as cardiovascular and sudden death mortality. The diagnosis of PCD based on clinical criteria probably underestimates the presence of underlying OHD, as suggested by a small but definite risk of cardiovascular mortality.

Adult↗
PubMed1979

Computer diagnosis of supraventricular and ventricular arrhythmias. A new esophageal technique.

Computerized arrhythmia monitors recognize only a few of the significant arrhythmias and generally fail to detect arrhythmias of supraventricular origin. This is because conventional surface leads, which are sufficient for QRS recognition, are highly inadequate for automated P-wave detection. A new two-lead system, which includes a swallowable capsule-electrode for esophageal monitoring of atrial activity, is used in an on-line arrhythmia monitor. Three interval measurements (AA, AR and RR) and a QRS shape measurement provide the foundation for a detailed interpretation of each beat. Building on the single-beat analysis, a contextual diagnostic algorithm then recognizes and reports on-line the following arrhythmias: couplets, bigeminy, trigeminy, ventricular tachycardia, supraventricular tachycardia, atrial flutter, atrial fibrillation, ventricular tachycardia with retrograde conduction to the atria, first-degree block, second-degree block, Wenckebach periodicity, advanced block, third-degree block and sinus bradycardia.

Arrhythmias, Cardiac↗
PubMed1979

Failure of surgery in preexcitation. Correlation with pathologic findings.

A 37-year-old man with mitral stenosis and recurrent drug-resistant paroxysmal atrial fibrillation, paroxysmal supraventricular tachycardia, and preexcitation, underwent two surgical attempts to ablate an anomalous pathway (AP). Electrophysiologic study demonstrated a left posterior AP with a short antegrade refractory period. Epicardial mapping at the time of mitral valve replacement (left lateral thoracotomy) suggested a posterior right AP. Mitral valve replacement and incision of the left atrial wall failed to cure preexcitation. Epicardial mapping at a second operation (median sternotomy) demonstrated a subepicardial left posterior AP. Right atrial and atrial septal incisions failed to cure preexcitation. Serial section of the atrioventricular rings and conduction system demonstrated an intact left posterior anomalous atrioventricular muscle bundle with surgical incision placed above the plane of the mitral anulus.

Adult↗
PubMed1979

Paroxysmal supraventricular tachycardia induction in patients with Wolff-Parkinson-White syndrome.

In 54 patients with pre-excitation, 30 (56%) had inducible A-V re-entrant paroxysmal tachycardia. Of these 30, 20 had spontaneous paroxysmal tachycardia (four also had atrial fibrillation), four had spontaneous paroxysmal atrial fibrillation, five had a history of palpitation without arrhythmia, and one was asymptomatic. In 24 patients (44%), paroxysmal tachycardia was not inducible. Of these 24, none had documented paroxysmal tachycardia, four had atrial fibrillation, none had palpitation without arrhythmia, and 11 were asymptomatic. The incidence of documented paroxysmal tachycardia was higher in the patients with inducible tachycardia (P less than 0.001). Tachycardia induction was noted in 20 of 20 patients with spontaneous paroxysmal tachycardia, eight of 12 patients with paroxysmal atrial fibrillation, five of 14 patients with palpitation and no arrhythmia, and one of 12 asymptomatic patients. The frequency of ability to induce paroxysmal tachycardia was significantly higher in both the patients with documented spontaneous paroxysmal tachycardia and the patients with paroxysmal atrial fibrillation than in the asymptomatic group (P less than 0.01).

Adolescent↗
PubMed1978

Clinical, electrocardiographic and electrophysiologic observations in patients with paroxysmal supraventricular tachycardia.

Seventy-nine patients without ventricular preexcitation but with documented paroxysmal supraventricular tachycardia were analyzed. Electrophysiologic studies suggested atrioventricular (A-V) nodal reentrance in 50 patients, reentrance utilizing a concealed extranodal pathway in 9, sinus or atrial reentrance in 7 and ectopic automatic tachycardia in 3. A definite mechanism of tachycardia could not be defined in 10 patients (including 7 whose tachycardia was not inducible). The three largest groups with inducible tachycardias were compared in regard to age, presence of organic heart disease, rate of tachycardia, functional bundle branch block during tachycardia and relation of the P wave and QRS complex during tachycardia. A-V nodal reentrance was characterized by a narrow QRS complex and a P wave occurring simultaneously with the QRS complex during tachycardia. Reentrance utilizing a concealed extranodal pathway was characterized by young age, absence of organic heart disease, fast heart rate, presence of bundle branch block during tachycardia and a P wave following the QRS complex during tachycardia. Sinoatrial reentrance was characterized by frequent organic heart disease, a narrow QRS complex and a P wave in front of the QRS complex during tachycardia. In conclusion, a mechanism of paroxysmal supraventricular tachycardia could be defined in most patients. Observations of clinical and electrocardiographic features in these patients should allow prediction of the mechanism of the tachycardia.

Adolescent↗
PubMed1978

Self-initiated conversion of paroxysmal atrial flutter utilizing a radio-frequency pacemaker.

A patient is described with drug-resistant recurrent paroxysmal atrial flutter. Electrophysiologic studies demonstrated that flutter was inducible with rapid atrial stimulation (stimulation rates of 375 to 400/min) and convertible with rapid atrial stimulation (rates of 400 to 460/min). Because of the latter response, a radio-frequency atrial pacemaker was implanted, which allowed self-initiated conversion of flutter episodes with rapid stimulation.

Arrhythmias, Cardiac↗
PubMed1978

Significance of left axis deviation in patients with chronic left bundle branch block.

Forty-nine patients with chronic left bundle branch block and a normal frontal axis were compared with 53 patients with left bundle branch block and left axis deviation. The following clinical variables were more frequent (P less than 0.05) in patients with left axis deviation: greater age, exertional angina, congestive heart failure, cardiomegaly, cardiac functional class II to IV, coronary artery disease and presence of organic heart disease. Absence of organic heart disease (primary conduction disease) was seen only in patients with a normal axis. Patients with left axis deviation had longer (P less than 0.05) mean P-R, A-H and H-V intervals and atrial and atrioventricular (A-V) nodal effective refractory periods. All patients were prospectifely followed up for 30 to 2,271 days with a mean +/- standard error of the mean follo-up period of 538 +/- 72 for the group with a normal axis and 604 +/- 72 days for the group with left axis deviation (difference not significant). A-V block developed in three patients (6 percent) with left axis deviation and in none of those with a normal axis. The cumulative 4 year mortality rate for the entire group approached 75 percent. The patients with left axis deviation had greater cardiovascular mortality (P less than 0.05). In conclusion, among patients with left bundle branch block, those with left axis deviation have a greater incidence of myocardial dysfunction, more advanced conduction desease and greater cardiovascular mortality than those with a normal axis.

Bundle-Branch Block↗
PubMed1978

Retrograde block during dual pathway atrioventricular nodal reentrant paroxysmal tachycardia.

There are limited reported data regarding the occurrence of retrograde block during dual pathway atrioventricular (A-V) nodal reentrant paroxysmal tachycardia. This study describes two patients with this phenomenon. The first patient had 2:1 and type 1 retrograde ventriculoatrial block during the common variety of A-V nodal reentrance (slow pathway for anterograde and fast pathway for retrograde conduction). Fractionated atrial electrograms suggested that the site of block was within the atria. The second patient had type 1 retrograde block (between the A-V node and the low septal right atrium) during the unusual variety of A-V nodal reentrance (slow pathway for retrograde and fast pathway for anterograde conduction). The abolition of retrograde block by atropine suggested that the site of block was within A-V nodal tissue. Both cases demonstrate that intact retrograde conduction is not necessary for the continuation of A-V nodal reentrant paroxysymal tachycardia. Case 2 supports the hypothesis that the atria are not a requisite part of the A-V nodal reentrant pathway.

Atrioventricular Node↗