Left ventricular dimensions and function during exercise in dogs with chronic right ventricular pressure overload

Left ventricular (LV) dimensions and shortening at rest and during treadmill exercise were examined before and after 4 weeks of pulmonary artery (PA) constriction in 6 conscious dogs. The dogs were preinstrumented with LV and right ventricular (RV) catheters, an LV micromanometer, a PA inflatable cuff occluder and ultrasonic crystals to measure an LV anteroposterior, a septal-lateral, an apex-base and a free wall segment chord. With PA constriction, RV pressures increased from $\text{49 ±}\text{4}\text{2}\text{± 1 mm}$ Hg (systolic/end-diastolic) to $\text{104 ±}\text{5}\text{2}\text{± 1}$ at rest and from $\text{71 ±}\text{9}\text{2}\text{± 1}\text{to}\text{133 ±}\text{8}\text{14}\text{± 2}$ at peak exercise (mean ± standard error of the mean). Heart rate, LV pressure and LV dP/dt were similar before and after RV pressure overload at rest and with exercise. During exercise at control, systolic shortening increased significantly in all chords. With chronic PA constriction at rest, shortening of all chords also remained normal despite decreases in end-diastolic dimensions, which were most marked in the septal-lateral chord (23% decrease, p <0.01). However, during exercise in the presence of RV pressure overload, septal-lateral shortening decreased 46% (p <0.01) despite increases in systolic shortening in the other chords similar to the control response. Therefore, although LV function at rest in chronic RV pressure overload is normal, exercise may induce regional abnormalities of LV contraction that appear to be mediated by a reduced contribution of the ventricular septum to LV ejection.     

Trends in epidemiology and patho-anatomical pattern of proximal humeral fractures

Purpose

Proximal humeral fractures are common and frequently associated with osteoporosis. Little is known about the association between the patho-anatomical fracture pattern of proximal humeral fractures and patient characteristics. The purpose of this six year longitudinal registry analysis of proximal humeral fractures was to study overall numbers, certain predefined pathoanatomical patterns and distribution compared with specific patient characteristics.

Methods

Data of patients treated between 2006 and 2011 in a country hospital that provides care >95 % of the city’s hospitalised patients with fractures was retrospectively reviewed. Data were analysed according to patient characteristics of age, gender, comorbidity, accompanying injuries and radiological analysis of pathoanatomical fracture patterns based on Neer and Arbeitsgemeinschaft für Osteosynthesefragen (AO) classification.

Results

Eight hundred and fifteen proximal humeral fractures (67 % women/33 % men; mean age 66 years, range 19–99) were analysed. During the study period, an overall increase of 42.5 % was found: according to AO classification, 46 % were type A, 22 % type B and 32 % type C. Based on the Neer classification, 86 % were displaced, and 49 % were complex with more than three parts. Of complex fractures, 57 % were female patients >60 years. The number of complex fractures was five times higher in women >60 years than in men of the same age group.

Conclusions

An overall increase of inpatients with displaced proximal tibial fractures was documented. Interestingly, complex displaced proximal humeral fractures, especially in older women with comorbidities, accounted for the majority of cases. These results suggest that health-care planning and hospital-based therapeutic strategies should focus on this patient group.     

Erfahrungen mit winkelstabilen Implantaten an Brust- und Lendenwirbelsäule

Internal fixators have long been used as fixed-angle implants for dorsal intrumentation of fractures of the thoracolumbar transition in the spine. After such dorsal intrumentation, even while the implants were still in place but even more after their removal, loss of correction has frequently been observed. Dorso-ventral spondylodesis provides a higher stability and is now increasingly frequently applied in the treatment of fractures of the thoracic and lumbar spine. Few data are available on the fusion rate of bone grafts. Early experience with fixed-angle implants that can be inserted in minimally invasive procedures are convincing. Further studies are needed to test whether these implants provide enough stability for ventrale spondylodesis without dorsal tension band instrumentation.     

Hemodynamic effects of n-acetylprocainamide compared with procainamide in conscious dogs

We examined the hemodynamic actions of clinically relevant i.v. doses (20 mg/kg and 10 mg/kg) of n-acetyl procainamide (NAPA) in conscious dogs preinstrumented with a left ventricular (LV) micromanometer, LV and aortic catheters, and ultrasonic crystals for measurement of LV internal diameter shortening (% delta D). Within 30 seconds after the 20-mg/kg dose, there were significant increases in heart rate (27 +/- 7 beats/min, mean +/- SEM; n = 6), maximum dP/dt (655 +/- 206 mm Hg/sec), and % delta D (2.2 +/- 0.9%; all p less than or equal to 0.05). However, by 6 hours after the dose there were reductions compared with control in peak LV pressure (19 +/- 9 mm Hg), dP/dt (610 +/- 210 mm Hg/sec), and % delta D (2.3 +/- 0.6%; all p less than or equal to 0.05). In contrast, equimolar doses of procainamide or drug vehicle alone evoked no response, as did NAPA after pretreatment with reserpine (0.25 mg/kg/day for 2 days) or hexamethonium (10-15 mg/kg). These data suggest NAPA produces a biphasic hemodynamic response with enhancement of LV performance early and a decrease later; this response is different from that of the parent compound, procainamide. These effects are likely mediated by the adrenergic nervous system at either a ganglionic or a central level.     

Left ventricular geometry during positive end-expiratory pressure in dogs

We evaluated changes in left ventricular (LV) geometry in ten dogs during intermittent positive-pressure ventilation (IPPV) with and without 10 cm H2O of positive end-expiratory pressure (PEEP). The dimensions during expiration and inspiration decreased in all three orthogonal axes during PEEP, consistent with decreased LV end-diastolic (ED) and end-systolic (ES) volumes. Within a respiratory cycle, the anterior-posterior (AP) ED dimension during inspiration increased with IPPV alone but decreased when PEEP was added, consistent with presumed differences in pulmonary venous return. This caused opposite changes in AP percent regional shortening. Septal-lateral free wall (SL) percent regional shortening decreased during inspiration with both IPPV and PEEP, but the respiratory variation was significantly less during PEEP. Thus, PEEP did not simply produce a smaller version of the same events seen during IPPV alone. The larger decreases with PEEP observed in ED compared to ES dimensions in the AP and SL axes suggest a dominant regional preload effect, whereas the larger fall in the long axis ES compared to ED dimension suggests a primary regional decrease in afterload. Measurements of the right ventricular SL axis in three dogs showed an overall reduction with PEEP, with the inspiratory dimensions being minimal during both IPPV alone and with PEEP. Thus, ventricular interdependence cannot account for the diminished LV SL dimension with PEEP during any part of the respiratory cycle. These findings suggest that the motion of the LV free wall influenced by changes in lung volume may be at least as important as septal motion in determining LV geometry with PEEP.(ABSTRACT TRUNCATED AT 250 WORDS)     

Refrakturen nach Entfernung von Osteosynthesematerialien

Refractures of long bones after implant removal are a rare but serious complication, which in most cases make a reoperation necessary. We analysed our own cases and reviewed the scarce literature on this subject. As a result we found that it is possible to reduce this complication by performing thorough preoperative preparation, observing an adequate interim time between initial osteosynthesis and hardware removal, cautiously exposing the weakened bone to force for a certain time period after implant removal and taking the character of the fracture healing into consideration. It is not possible to entirely eradicate this complication because a lot of patients demand the implant removal even though it is known that demineralisation and residual screw holes both induce a reduction of energy-absorbing capacity and therefore predispose the patient to refracture. In some cases the surgeon should recommend that the implants remain in situ.     

Begleit- und Nachbehandlung bei HWS-Distorsionen

Postulating that a whiplash injury leads to a muscular imbalance of the neck muscles, we developed a therapy concept based on self-training of the patient with the support of specialists. This concept was evaluated in a prospective pilot study involving 45 patients. The results of the follow-up checks carried out 2 and 4 weeks and again 6 months after the injury showed good acceptance of the self-training programme, and a symptomatic recovery was achieved in most of the patients.     

Effects of postural bias during support surface displacements and rapid arm movements

The purpose of this study was to evaluate body-sway characteristics during anticipatory and reactive postural compensation. Mechanisms of postural control were studied during self-initiated rapid arm movements (RAMs) and unexpected support surface displacements (SSDs). Ten healthy subjects, 5 men and 5 women with a mean age of 28 years, were blindfolded and stood symmetrically on a moveable force platform or with weight shifted right (R) or left (L). Averaged electromyographs were obtained from L anterior deltoid, L ipsilateral biceps femoris (BFi), R contralateral biceps femoris (BFc), R quadriceps (Q), R medial gastrocnemius (G), and R tibialis anterior (TA) muscles. During SSD, the relative timing of distal-proximal synergists was altered during all biased postures. In L biased standing, functional pairs, TA-Q and G-BF, discharged at their shortest latencies. Anterior deltoid onset times during RAM were most preparatory during R weight shift. Sway latencies were shorter also in biased standing. Absolute sway latency, peak sway, and time-to-peak sway were significantly longer in SSD conditions in comparison with RAM. When disturbances in balance cannot be predicted, lower extremity preloading facilitates contralateral muscle-discharge patterns at shorter latencies. In some neurological conditions that result in incorrect body alignment, the mechanical effects of postural bias rather than the abnormal control mechanisms may at least contribute to alterations in the postural response. These results provide a basis for evaluating balance in patients with neurological deficit.