An integrated overview of AV node physiology

The atrioventricular (AV) node generates half of the AV delay needed for blood pumping and filters atrial impulses that could otherwise induce life‐threatening ventricular arrhythmias. It is also a pacemaker and a key target in the treatment of cardiac arrhythmias. The special roles of the AV node primarily arise from its slow conduction, long refractory period, and cellular automaticity. However, efforts to establish the dynamics of these properties and their interaction led to many controversies. In fact, the AV node's behavior is so complex that it seems to escape broadly applicable rules. This review summarizes progresses made in resolving these issues and in integrating the multiple roles of the AV node within a common functional model. Presented evidence shows that the rate‐dependent conduction and refractory properties of the AV node can be reliably characterized and reconciled from nodal responses to S₁S₂S₃ protocols. It also supports the concept that dual pathways constitute a feature of the normal AV node and account for its overall conduction and refractory properties. In this model, the posterior extension and compact node provide the core of the slow and fast pathway, respectively. The transitional tissues and lower nodal bundle provide a common proximal and distal pathway, respectively. These pathways would also support bidirectional conduction. The dual pathway involvement can also be extended to widely variable AV nodal responses, such as Wenckebach cycles, hysteresis, and ventricular response to atrial fibrillation. In brief, the intricate AV nodal behavior may obey a limited set of accessible and definable rules.     

An unusual combination of floating knee and trifocal articular tibial fracture

Fractures of the ipsilateral femur and tibia are a devastating injury complex, usually as the consequence of high-energy traumatisme. We present a case of 42-year-old man, who sustained a simultaneous fracture of the femoral shaft and trifocal tibia. Our management consisted of treating both the femoral and the tibial fractures surgically, by intramedullary nailing and a percutaneous screw fixation of tibial and malleolar fracture. He was evaluated at 4 years of follow-up. With careful attention to some technical points, femoral fracture, ipsilateral tibial plateau, shaft and malleolar fractures can be managed successfully by combining two familiar techniques commonly employed for each injury in isolation.     

Les torsions sur testicules cryptorchides

Purpose:

Cryptorchidism is a rather frequent pathology in urology. It is associated with a high risk of infertility and degeneration. It also seems to be associated with a high risk of torsion. This entity is poorly studied in the literature. We studied the cases of torsion on cryptorchid testicles hospitalized at our service, to better characterize this pathology and reduce the rate of orchidectomy.

Methods:

We underwent a retrospective study of all the cases of torsion on a cryptorchid testicle hospitalized in our service of urology between 1999 and 2007.

Results:

The age of patients was between 7 months and 39 years. Torsion touched the right testicle in 53% of the cases. Patients experienced a brutal pain of the inguinal area with an under cutaneous mass inflammatory and a painful and empty homolateral scrotum. In 60% of the cases, the diagnosis was late and an orchidectomy was carried out. In the other cases, a lowering of the testicle was done with the controlateral orchidopexy.

Conclusion:

Even though torsions on a cryptorchid testicle are rare, we should not ignore them. The early diagnosis will make it possible to save and lower the testicle, and track a possible degeneration.     

Hepatitis A in Tunisia: phylogenetic analysis of hepatitis A virus from 2001 to 2004

Tunisia is a highly endemic area for hepatitis A virus (HAV) infection. In the present study, the phylogenetic characterization of the VP1 gene (882 nucleotides) and of the VP1/2A junction (336 nucleotides) of Tunisian strains were examined. One hundred strains isolated from patient with anti-HAV IgM from 2001 to 2004 were amplified by RT-PCR, sequenced at the VP1 and at the VP1/2A junction and aligned with the published sequences to establish phylogenetic analysis. All Tunisian strains belong to genotype I with a greater presence of sub-genotype IA (98%) originate from most of Tunisian regions and 2% of sub-genotype IB. In addition, sub-genotype IA and IB strains formed 25 different clusters. Genetically similar strains were also identified between 2001 and 2004 isolated from the southern and the central part of Tunisia, suggesting that an indigenous strain has been circulating in the Tunisia. The genetic profile of the VP1 region showed that Tun159-02 and Tun40-03 clustered respectively in the IB and IA sub-genotype, however, analysis of VP1/2A junction revealed in contrast that Tun159-02 and Tun40-03 clustered respectively in IA and IB. This is the first report to identify sub-genotype IA in Tunisia and provides new data on the genetic relatedness of HAV from Tunisia and the distribution of sub-genotype IA in this part of the world.     

Metastatic tumors in the jaws: a retrospective study of 114 cases

BACKGROUND: Malignancies involving the bones are metastatic tumors more commonly than primary tumors. In this retrospective study, the authors review metastatic disease in the jaws. METHODS: The authors retrieved cases of metastatic disease in the jaws over a 45-year period from the pathology archives at the University of Michigan School of Dentistry, Ann Arbor, and Indiana University School of Dentistry, Indianapolis. RESULTS: The authors conducted a retrospective analysis of 114 cases of metastatic disease in the jaws and found that approximately 60 percent of subjects had no history of malignancy. The sex distribution was equivalent. Mandibular predilection was more prominent in females than in males. Metastases from the breast were significantly greater than those from the lung and prostate (P < or = .05), the second and third most frequent sites, respectively. Women exhibited twice as many jaw metastases as did men 31 to 40 years of age and significantly fewer metastases than did men 71 to 80 years of age (P < or = .05). CONCLUSION: In the majority of cases, subjects had an undiagnosed primary cancer at the time the metastatic jaw disease presented. The most common site of origin of the primary cancer was the breast, when primary sites were considered independent of sex. CLINICAL IMPLICATIONS: Patients with metastatic disease in the jaws may have innocuous dental symptoms, such as pulpal or periodontal pain; therefore, clinicians will play a significant role in diagnosing the life-threatening disease.     

Prospective cohort study of HIV post-exposure prophylaxis for sexual assault survivors

BACKGROUND: There is a lack of standardized programs for HIV counselling and post-exposure prophylaxis (PEP) in the setting of sexual assault. METHODS: We conducted an 18-month prospective cohort study assessing universal HIV counselling for all sexual assault survivors presenting to 18 Ontario Sexual Assault Treatment Centres. HIV PEP was universally offered to those at risk of HIV infection (high risk or unknown risk) presenting < or =72 h after the assault, using Combivir one pill and Kaletra three capsules twice a day for 28 days. Those who accepted HIV PEP were monitored via a schedule of frequent follow ups. The primary outcomes were acceptance and completion rates, and their predictors were determined using multivariable logistic regression. Adverse events (AE) were categorized using a standardized toxicity grading system. RESULTS: Of the 900 evaluable participants eligible for PEP, 798 (69 at high risk and 729 at unknown risk) were offered treatment. Acceptance rates were 66.7% (n=46) and 41.3% (n=301) for participants at high risk and unknown risk, respectively. Participants at high risk were 2.2 times more likely to accept PEP than those at unknown risk (adjusted odds ratio 2.2; 95% confidence interval 1.2-4.0; P=0.01). Overall, 23.9% high-risk (n=11) and 33.2% unknown-risk participants (n=100) completed PEP (P=0.20). Predictors of acceptance and completion included assault by a stranger and participant anxiety. AEs were common, with 77.1% of participants reporting grade 2-4 symptoms. CONCLUSION: A province-wide standardized program of universal HIV counselling and offering of PEP to sexual assault survivors with frequent follow up was successfully implemented and feasible.     

Safety of furosemide administration in an elderly woman recovered from thiazide-induced hyponatremia

BackgroundElderly women are at risk to develop severe hyponatremia after thiazide but not loop diuretic administration. In patients with previous thiazide-induced hyponatremia, the risk for recurrent hyponatremia after furosemide has not been established.MethodsIn order to determine how both diuretics affect water metabolism, we here compare the effects of a rechallenge with either amiloride-hydrochlorothiazide fixed association (AmHTZ; amiloride chlorhydrate 5 mg + hydrochlorothiazide 50 mg; Moduretic?) or furosemide (F; 40 mg; Lasix?) on water excretion in a 79 year old woman who was previously admitted for severe symptomatic hyponatremia secondary to a 5 days course of AmHTZ for systolic hypertension. After correction of initial hydromineral disturbances, a standard oral water load (WL; 20 mL per kg body weight) was administered before, during and after AmHTZ or F challenges.ResultsHyponatremia developed after AmHTZ but not after F challenge. A negative free water clearance (CH₂O) was only observed during AmHTZ (? 0.39 mL/min), while maximal CH₂O during F was 3.17 mL/min. Based on the results obtained during WL, the calculated maximal daily electrolyte free water clearance ability was only 888 mL after AmHTZ but 10,166 mL after F therapy. Taking into account a measured mean daily water intake of 1830 mL, severe hyponatremia could be predicted to occur after a few days treatment with AmHTZ. In comparison, F appears to be safer, without risk of hyponatremia, during an equivalent period of time.ConclusionsWe here showed that F may be administered to a patient with previous AmHTZ induced hyponatremia without risk for recurrent hyponatremia.     

Antiretroviral therapy 2000

As we enter the new millennium, there have been dramatic improvements in the care of patients with HIV infection. These have prolonged life and decreased morbidity and mortality. There are fourteen currently available antiretrovirals approved in the United States for the treatment of this infection. The medications, including their pharmacokinetic properties, side effects, and dosing are reviewed. In addition, the current approach to the use of these medicines is discussed.