Successful Delivery in a Patient With Left Ventricular Assist Device and Unplanned Pregnancy.

We report the case of a woman supported by a left ventricular assist device (LVAD) who presented at 20 weeks of gestation and decided against recommendations to continue with her pregnancy. This was managed with well-developed plan for a multidisciplinary team approach. With close and regular follow-up and regular adjustment of the patient's medications and LVAD parameters, successful delivery and outcome for both the mother and the newborn were achieved.

The possible role of arterial radial vibration in heart rate and blood pressure matching.

MOTIVATION: This study tests if the 'oscillating spring' analogy for the radial vibration of the arterial wall can help to describe the relationship between the heart rate (HR), the blood pressure (BP), and properties of the arterial wall when different types of stimulation are applied on the cardiovascular system. It may help to suggest a possible role for arterial radial vibration in the association between the arterial stiffening and hypertension. METHODS: Either mechanical stimulation was applied (0.5-mmHg pressure variation) to Wistar rats by at near-HR frequency (group A) or administered Propranolol (2mg/kg i.p.; group B), and measured HR and BP simultaneously. RESULTS: In both groups, HR and BP were noted to change in the same direction (r2 = 0.72 and 0.62, respectively; p both < 0.05 by F-test). ANCOVA was performed on these two regression lines, and it was found that there was no significant difference between them (p > 0.3). CONCLUSION: In both groups, changes in haemodynamic parameters can be explained by the 'oscillating spring' analogy for the radial vibration of the arterial wall. This illustrates that, when facing various stimulations, it may be an important regulatory mechanism for the heart and the arteries to restore their frequency-matching condition in order to improve the arterial transmission efficiency. Paying more attention to the radial movement of the wall may therefore help to suggest a novel explanation of the mechanism that underlies the bidirectional relation between hypertension and arterial stiffening.

Evaluating microcirculation by pulsatile laser Doppler signal.

Laser Doppler flowmetry (LDF) is a popular method for monitoring the microcirculation, but it does not provide absolute measurements. Instead, the mean flux response or energy distribution in the frequency domain is generally compared before and after stimulus. Using the heartbeat as a trigger, we investigated whether the relation between pressure and flux can be used to discriminate different microcirculatory conditions. We propose the following three pulsatile indices for evaluating the microcirculation condition from the normalized pressure and flux segment with a synchronized-averaging method: peak delay time (PDT), pressure rise time and flux rise time (FRT). The abdominal aortic blood pressure and renal cortex flux (RCF) signals were measured in spontaneously hypertensive rats (SHR) and Wistar Kyoto rats (WKY). The mean value of the RCF did not differ between SHR and WKY. However, the PDT was longer in SHR (87.14 +/- 5.54 ms, mean +/- SD) than in WKY (76.92 +/- 2.62 ms; p < 0.001). The FRT was also longer in SHR (66.56 +/- 1.98 ms) than in WKY (58.02 +/- 1.77 ms; p < 0.001). We propose that a new dimension for comparing the LDF signals, which the results from the present study show, can be used to discriminate RCF signals that cannot be discriminated using traditional methods.

Effects of whole-body mechanical stimulation at double the heart rate on the blood pressure waveform in rats.

The effects of mechanical stimulation on hemodynamics, such as due to mechanotransduction in vascular endothelial cells, have been widely discussed recently. We previously proposed a resonance model in which the arterial system is treated as a pressure-transmitting system, and suggested that the application of external mechanical stimulation with frequencies near the heart rate (HR) or harmonics thereof can be sensed by the arterial system and induce hemodynamic changes. In this study, we monitored the effects of external mechanical stimulation at a frequency of double the HR on BPW (blood pressure waveform), HRV (HR variability) and BPHV (blood-pressure-harmonics variability) in rats. A motor beating a waterbed mattress was used to generate pressure variations of 0.5 mmHg to apply onto the rats. The experiments were performed on three groups of rats with different beating frequencies: (A) double the HR, (B) 5% deviation from double the HR and (C) 1.5 times the HR. The experimental procedure was a 15 min control period followed by application of the mechanical stimulation for 15 min and further recording for 15 min (OFF period). During the OFF period, the amplitude of the second harmonic in the BPW significantly increased by >5% in group A with decreased HRV and BPHV. The second harmonic increased less in group B, and decreased in group C. The increase in the second-harmonic amplitude in group A may be due to the filtering properties of the renal arterial structure. This mechanism could be used to improve the local blood supply into the kidneys, and hence provide a new treatment modality for some important diseases, such as renal hypertension or nephrosis.

Influencing the heart rate of rats with weak external mechanical stimulation.

The ventricular-arterial coupling is assumed to minimize the expenditure of cardiac energy. From the conjecture of the resonance theory, the arterial system transmits pressure waves and resonates with the heartbeat, therefore, the arterial system is similar to a mechanical resonator. Theoretically, the heart rate can be paced with weak external mechanical stimulation and corresponding blood pressure changes can be observed. A waterbed was activated to generate 0.5-mmHg pressure vibrations as a stimulus and the rate was set to deviate 5% from the control heart rate. Among 13 studies on seven rats, the linear regression between X (stimulation frequency--control heart rate) and Y (actual changes of the heart rate) is Y = 0.992X = 0.062 (Hz) with a correlation coefficient of 0.97 (Y = X implies complete steering). The intercorrelation coefficient between the change in mean blood pressure and the heart rate was 0.79. The study showed that this weak mechanical stimulation influences the heart rate, and the blood pressure changes according to the heart rate. Cardiovascular optimization and the resonance theory may explain the way one may regulate the heart rate and the blood pressure of humans noninvasively in the future.

Effect of length on the fundamental resonance frequency of arterial models having radial dilatation.

The pressure wave moving along an elastic artery filled with blood was examined as a moving Windkessel having a natural oscillation angular frequency nu 0 and a damping coefficient b. The radial directional motion for an element of the wall segment and the adherent fluid was considered. This equation was solved with conditions at both ends of an artery of length L. An external impulse force was applied at one end and a static pressure Po at the other. Analytic solution allowed only certain oscillation modes of resonance frequencies fn, where fn2 = a + cnL-2 with [formula: see text] and V infinity is the high frequency phase velocity. The relationship between f0 and L was examined experimentally for tubes constructed of latex, rubber, or dissected aorta. The effect of raising the static pressure P0 or increasing the tension in the tube was consistent with the prediction. The hypertension that accompanies an augmentation in arterial wall and the association between the heart rate and the mean blood pressure were discussed.

Anthropometric standards in normal Saudi newborns at sea level.

Normal anthropometric standards are presented for Saudi newborns at sea level between 38 and 42 weeks' gestation with a mean gestation age of 40.0 weeks for boys and 40.1 weeks for girls. These standards are based on cross-sectional measurements performed by the author and well-instructed nurses using standard measurement techniques. Each set of observations was normally distributed, except the head circumference of the girls, which was bimodal. A significant correalation was found between the five parameters when taken in pairs. Mean, standard deviation, and centiles were calculated. The results obtained in this study are presented and compared with national and international data. The need for a national study of perinatal growth is emphasized.