2:1 atrioventricular block during atrioventricular node reentrant tachycardia

OBJECTIVES

The purpose of this study was to determine the incidence and to clarify the mechanism of 2:1 atrioventricular (AV) block during AV node reentrant tachycardia induced in the electrophysiology laboratory.

BACKGROUND

In patients with 2:1 AV block during AV node reentrant tachycardia, the absence of a His bundle potential in the blocked beats has been considered evidence of intranodal, lower common pathway block.

METHODS

In consecutive patients with AV node reentrant tachycardia, the incidence of 2:1 AV block and the response to atropine and a single ventricular extrastimulus was observed.

RESULTS

Persistent 2:1 AV block occurred in 13 of 139 patients with AV node reentrant tachycardia. A His bundle deflection was present in the blocked beats in eight patients and absent in five. Patients with 2:1 AV block had a shorter tachycardia cycle length than did patients without such block (mean +/- SD 312 +/- 32 vs. 353 +/- 55 ms, p < 0.01). Atropine did not alter the 2:1 block in any patient. In every patient, a single ventricular extrastimulus introduced during the tachycardia converted the 2:1 block to 1:1 conduction.

CONCLUSIONS

The incidence of induced 2:1 AV block during AV node reentrant tachycardia is approximately 10%. The lack of a response to atropine and the consistent conversion of 2:1 block to 1:1 conduction by a ventricular extrastimulus indicate that, regardless of the presence or absence of a His bundle potential in blocked beats, 2:1 block during AV node reentrant tachycardia is due to functional infranodal block.

The effects of age, gender, and season on serotonergic function in healthy subjects

1. Several factors, including age, gender, and season of the year, have been reported to affect physiologic indices of central serotonergic function, although some of these findings have not been consistent across groups of subjects and types of serotonergic measures. 2. The authors investigated the role that each of these variables might play in the neuroendocrine response to acute intravenous challenge with the serotonin reuptake inhibitor clomipramine (CMI) in healthy volunteers. 3. Thirty seven healthy subjects (17 women and 20 men), with an age range of 19 to 50 years, received 12.5 mg of CMI intravenously under standardized conditions. 4. The maximum change from baseline in plasma prolactin concentrations ("delta-max") was significantly related to age, after controlling for gender and season. 5. In contrast, neither gender nor season was significantly related to prolactin delta-max, after controlling for the other two variables. 6. Although the age range and sample size are relatively limited, the results from this study suggest that age, but not gender or season, may influence serotonergic function, as measured by the prolactin response to CMI challenge.

Comparison of atrial-His intervals in patients with and without dual atrioventricular nodal physiology and atrioventricular nodal reentrant tachycardia

The purpose of this study was to compare the atrial-His intervals generated during programmed atrial stimulation in patients with and without dual atrioventricular nodal physiology and with and without inducible atrioventricular nodal reentrant tachycardia. Programmed atrial stimulation at a basic-drive cycle length of 500 to 600 msec was performed in 180 patients. The minimum atrial-His interval was defined as the atrial-His interval of the basic-drive beats. The maximum atrial-His interval was defined as the longest A2H2 interval. The criterion for dual atrioventricular nodal physiology was an increment of 50 msec in the A2H2 interval in association with a 10 msec decrement in the A1A2 interval. The minimum atrial-His interval was significantly shorter (106 +/- 34 msec vs 116 +/- 29 msec; p < 0.05) and the maximum atrial-His interval significantly longer (304 +/- 101 msec vs 222 +/- 56 msec; p < 0.001) in the 87 patients who had atrioventricular nodal reentry than in the 93 patients who did not. Among the 87 patients who had atrioventricular nodal reentry, the maximum atrial-His interval was significantly longer in 53 patients who had dual atrioventricular nodal physiology than in 34 patients who did not (340 +/- 105 msec vs 249 +/- 62 msec; p < 0.001). Among the 66 patients who had dual atrioventricular nodal physiology, the maximum atrial-His interval was significantly longer in 53 patients who had atrioventricular nodal reentry than in 13 patients who did not (340 +/- 105 msec vs 268 +/- 61 msec; p < 0.01). The insensitivity of the conventional dual atrioventricular nodal physiology criterion for the detection of dual atrioventricular nodal pathways is in part attributable to a lesser degree of slowing of conduction in the slow pathway relative to the fast pathway in some patients who have atrioventricular nodal reentry. The inability to demonstrate atrioventricular nodal reentry despite the presence of dual atrioventricular nodal physiology in some persons may be attributable in part to an inadequate degree of conduction delay in the slow pathway.

Slow pathway ablation in patients with documented but noninducible paroxysmal supraventricular tachycardia

OBJECTIVES

The purpose of this study was to assess the clinical efficacy of radiofrequency ablation of the slow pathway in patients with documented but noninducible paroxysmal supraventricular tachycardia (PSVT) who have evidence of dual atrioventricular (AV) node pathways.

BACKGROUND

Patients with a documented history of PSVT at times do not have inducible PSVT in the electrophysiology laboratory. Because dual AV node pathways serve as the substrate for AV node reentrant tachycardia (AVNRT), ablation of the slow pathway potentially may be useful in these patients.

METHODS

The subjects in this prospective study were seven consecutive patients who underwent an electrophysiologic procedure because of documented PSVT and were found to have dual AV node physiology or inducible single AV node echo beats, but no inducible PSVT despite the administration of isoproterenol and atropine. Their mean (+/- SD) age was 33 +/- 13 years, and they had been symptomatic for 12 +/- 12 years. The frequency of the episodes of PSVT ranged from > or = 1/day to 1/month. The rate of the documented episodes ranged from 170 to 260 beats/min, and discrete P waves were not apparent. Slow pathway ablation was performed with 9 +/- 4 applications of radiofrequency energy using a combined anatomic and electrogram mapping approach.

RESULTS

All evidence of dual AV node pathways was eliminated in six patients, and dual AV node physiology remained present in one patient. During a mean follow-up period of 15 +/- 10 months (range 8 to 27), no patient had a recurrence of symptomatic tachycardia (success rate 95% confidence interval 65% to 100%).

CONCLUSIONS

Slow pathway ablation may be clinically useful in patients with documented but noinducible PSVT who have evidence of dual AV node pathways.

Ligneous conjunctivitis in four Doberman pinschers

Ligneous conjunctivitis (LC) was diagnosed in four unrelated Doberman pinschers. Thick, opaque membranes of the palpebral conjunctivae and nictitating membranes were present bilaterally. Three dogs had concurrent signs of multisystemic disease. A thick, amorphous, eosinophilic, hyaline-like material in the substantia propria of the conjunctiva--containing a moderate, mononuclear cell infiltrate--was evident on histological examination. A predominance of T lymphocytes, few macrophages, and weak positive staining for immunoglobulin G (IgG) and immunoglobulin A (IgA) were evident by immunohistochemical staining. The clinical and histological appearance of LC in Doberman pinschers and humans is similar.

Ophthalmic manifestations and complications of dental disease in dogs and cats

Ophthalmic manifestations of dental disease may occur in dogs and cats because of the proximity between posterior maxillary teeth and the orbit. Ophthalmic disorders may be diagnosed promptly, but the initiating dental disease may be overlooked. Inappropriate diagnosis and treatment of dental disease may result in loss of teeth, irreversible vision-threatening ophthalmic disease, or, ultimately, loss of the globe. When ophthalmic examination results are suggestive of a primary dental disorder, thorough examination of the maxillary teeth is imperative to diagnose appropriately the underlying dental disease. Therapy should include treatment of the dental disease and secondary ophthalmic disorders.

Locally acquired Brachylaima sp. (Digenea: Brachylaimidae) intestinal fluke infection in two South Australian infants

Eggs of a small intestinal trematode were found in the faeces of two 21-month-old children from the same rural district of South Australia who presented 18 months apart with mild abdominal pain and diarrhoea. Treatment with praziquantel resulted in egg clearance and resolution of gastrointestinal symptoms. A brachylaimid intestinal trematode involving the common house mouse, poultry and introduced European helicid snails is well established in South Australia. Both infants had been seen eating raw snails, and snails from their environment were found to be infected with metacercariae of a brachylaimid trematode.

Can cervical cancer be prevented by a see, screen, and treat program? A pilot study

OBJECTIVE

Our purpose was to determine the feasibility of providing a cervical screening facility to the underprivileged communities through an educational program and a mobile clinic in which cytologic smears could be taken, screened immediately, and, when appropriate, the patients treated on site with minimal delay.

STUDY DESIGN

A prospective study was conducted in two parts on 5045 patients living in squatter areas around Cape Town, South Africa. The patients were educated about cervical cancer and its prevention and were offered a free Papanicolaou smear taken in a fully equipped mobile clinic. These were immediately stained and processed. Patients diagnosed cytologically as having high-grade squamous intraepithelial lesions were assessed colposcopically and, when indicated, immediately treated by large loop excision of the transformation zone under local anesthesia.

RESULTS

In phase 1, colposcopy was done in the nearest colposcopy clinic, 20 km from the screening site. The defaulter rate was 66%. In phase 2, colposcopy and treatment were offered on site. A total of 97% of patients referred for colposcopy attended the clinic, and all patients requiring treatment have been adequately treated.

CONCLUSION

With a rapid turnaround time for the reporting of cytologic results and given a colposcopy and treatment facility available located at the screening site at the time women receive their results, the majority of women will undergo colposcopy and treatment.

A guide to writing medical reports on survivors of torture

Based on a number of years' experience by volunteer doctors engaged in the examination and welfare of refugees and asylum-seekers who have claimed that they have suffered torture a scheme of history-taking and physical examination is offered. The role of the medical expert in the investigation of abuse of human rights is discussed, as is the need for the presentation and format of the interpretation to be carefully considered.

Isolation of the Heterofullerene C59N as Its Dimer (C59N)2

The heterofullerene ion C(59)N(+) is formed efficiently in the gas phase during fast atom bombardment mass spectroscopy of a cluster-opened N-MEM (N-methoxyethoxy methyl) ketolactam. This transformation is shown to occur also in solution in the presence of strong acid, affording biazafullerenyl (C(59)N)(2) in good yield. It is proposed that the azafullerene dimer is formed upon in situ reduction of the highly reactive azafulleronium ion. The isolation and characterization of biazafullerenyl opens a viable route for the preparation of other heterofullerenes in solution.

Altered prolactin response to clomipramine rechallenge in healthy subjects

The effect of an initial challenge with the serotonin (5-HT) uptake inhibitor clomipramine (CMI) on subsequent rechallenge was studied in healthy men who served as volunteers. Carefully screened volunteers were assigned to one of three conditions: (1) CMI challenge followed 2 weeks later by CMI rechallenge; (2) placebo challenge followed 2 weeks later by CMI challenge; and (3) CMI challenge followed 4 weeks later by CMI rechallenge. We found significant blunting of the prolactin response to CMI rechallenge 2 weeks (Signed Rank = -12, p = 0.05), but not 4 weeks after an initial challenge. Placebo challenge did not effect CMI challenge 2 weeks later. These findings suggest that a single exposure to IV CMI may cause 5-HT receptor changes that are present 2, but not 4 weeks later. The ramifications of this finding with regard to the use of 5-HT challenge paradigms in a test-retest design are discussed.

Parachute-like sinus venosus remnant: echocardiographic and pathological appearance

A female infant with multiple congenital abnormalities and a right atrial "mass" on echocardiography is reported. Her general condition at birth was poor, and the chest x-ray showed cardiomegaly. Echocardiography demonstrated the usual atrial arrangement and concordant atrioventricular and ventriculoarterial connections with a mobile right atrial mass. Death occurred at 3 days of age and subsequent postmortem examination revealed a hollow, tube-like sinus venosus remnant mobile between right atrium and ventricle with numerous other abnormalities of the heart, including left heart hypoplasia and tubular hypoplasia of the aortic arch. Filling of the sinus venosus remnant with blood had resulted in an echocardiographic appearance suggestive of a right atrial tumor.

No-fault compensation and performance review

Two major issues in relation to medical malpractice are discussed. The first is "no-fault compensation", an alternative to the present tort system long established in most countries, including Singapore, where negligence must be proved before a claim can succeed. The second is "performance review", a new concept for monitoring and correcting under-performing medical practitioners against whom a complaint has been laid. Both these issues are currently under active discussion and are arousing political notice and professional controversy. Though the article describes the British situation, there is much of contemporary relevance for Singapore, which has such a similar system of medical practice.

Induction of adjuvant arthritis in mice

Adjuvant arthritis, induced by injections of Freund's complete adjuvant into the footpads of some rat strains, has been recognized as a useful animal model for many years. There has, however, been notable lack of success in reproducing this model in other species. We now describe the development of adjuvant arthritis in healthy strain mice approximately 2 months after injection of Freund's complete adjuvant. Although the clinical appearance of the mice and the joint histopathology closely resemble the adjuvant arthritis reported in the rat, we were unable to detect rheumatoid factor in sera from the affected animals. In parallel studies of T cell proliferation, affected animals responded to some mycobacterial antigens but not to the 65-kD heat shock protein of Mycobacterium tuberculosis, suggesting that some other epitope is important in the development of the disease.