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Venous obstructions and thrombosis can present diagnostic challenges due to their varied presentations and potential for significant complications if untreated. Pulse wave doppler ultrasound via identification of damping or loss of cardiac pulsatility and/ or respiratory phasicity of venous waveforms serves as a practical, noninvasive, fast, and efficient diagnostic tool for identifying venous obstructions in the presence of compressible veins beyond the point of evaluation. We present two cases demonstrating the effectiveness of pulse wave doppler ultrasound in identifying significant and life-threatening venous obstructions. The first case involves a 68-year-old male with an incidental finding of a compressible left subclavian vein showing a monophasic waveform. Further investigation revealed significant compression of the left brachiocephalic vein by an aortic arch aneurysm. The second case describes a 65-year-old male with a compressible right femoral vein but a monophasic waveform, leading to the discovery of extensive thrombosis from the iliac veins to the inferior vena cava. This series proposes to always assess cardiac pulsatility and respiratory phasicity during doppler ultrasound procedure such as thyroid ultrasounds, deep vein thrombosis (DVT) evaluations, and pre-central vein catheterizations for identifying any venous obstructions, whether they are intrinsic or extrinsic, and for reducing the risk of thromboembolic complications. [ABSTRACT FROM AUTHOR]

The application of biomimetic physical stimuli replicating the in vivo dynamic microenvironment is crucial for the in vitro development of functional cardiac tissues. In particular, pulsed electrical stimulation (ES) has been shown to improve the functional properties of in vitro cultured cardiomyocytes. However, commercially available electrical stimulators are expensive and cumbersome devices while customized solutions often allow limited parameter tunability, constraining the investigation of different ES protocols. The goal of this study was to develop a versatile compact electrical stimulator (ELETTRA) for biomimetic cardiac tissue engineering approaches, designed for delivering controlled parallelizable ES at a competitive cost. ELETTRA is based on an open-source micro-controller running custom software and is combinable with different cell/tissue culture set-ups, allowing simultaneously testing different ES patterns on multiple samples. In particular, customized culture chambers were appositely designed and manufactured for investigating the influence of monophasic and biphasic pulsed ES on cardiac cell monolayers. Finite element analysis was performed for characterizing the spatial distributions of the electrical field and the current density within the culture chamber. Performance tests confirmed the accuracy, compliance, and reliability of the ES parameters delivered by ELETTRA. Biological tests were performed on neonatal rat cardiac cells, electrically stimulated for 4 days, by comparing, for the first time, the monophasic waveform (electric field = 5 V/cm) to biphasic waveforms by matching either the absolute value of the electric field variation (biphasic ES at ±2.5 V/cm) or the total delivered charge (biphasic ES at ±5 V/cm). Findings suggested that monophasic ES at 5 V/cm and, particularly, charge-balanced biphasic ES at ±5 V/cm were effective in enhancing electrical functionality of stimulated cardiac cells and in promoting synchronous contraction.

Background: Peripheral arterial disease is defined as a clinical disorder in which there is a stenosis or occlusion of the arteries of the limbs. The most common etiology is ischemia due to occlusive disease. The objective of this study is to assess the severity of lower-limb peripheral arterial diseases based on various Doppler parameters. Methods: This descriptive cross-sectional study comprised 55 patients with clinical signs and symptoms of lower-limb peripheral arterial disease. Both inpatients and outpatients attending the authors' institute were taken up for the study. In this study, Doppler sonography was performed using 3–12 MHz linear array and 1–7 MHz curvilinear array transducers (SAMSUNG RS80A Ultrasound System). Results: Out of 55 patients, Doppler sonography demonstrated echogenic plaques in 32 patients and corkscrew collaterals in 15 patients. Monophasic waveform with peak systolic velocity ratio of >2:1 was found in 42 patients, which is consistent with significant stenoses. Conclusion: Our study shows that Duplex Doppler sonography aided by color Doppler sonography can accurately locate the site and severity of stenosis/occlusion. It is safe, cost-effective, repeatable, and noninvasive.

Background: Peripheral arterial disease is defined as a clinical disorder in which there is a stenosis or occlusion of the arteries of the limbs. The most common etiology is ischemia due to occlusive disease. The objective of this study is to assess the severity of lower-limb peripheral arterial diseases based on various Doppler parameters. Methods: This descriptive cross-sectional study comprised 55 patients with clinical signs and symptoms of lower-limb peripheral arterial disease. Both inpatients and outpatients attending the authors' institute were taken up for the study. In this study, Doppler sonography was performed using 3-12 MHz linear array and 1-7 MHz curvilinear array transducers (SAMSUNG RS80A Ultrasound System). Results: Out of 55 patients, Doppler sonography demonstrated echogenic plaques in 32 patients and corkscrew collaterals in 15 patients. Monophasic waveform with peak systolic velocity ratio of >2:1 was found in 42 patients, which is consistent with significant stenoses. Conclusion: Our study shows that Duplex Doppler sonography aided by color Doppler sonography can accurately locate the site and severity of stenosis/occlusion. It is safe, cost-effective, repeatable, and noninvasive. [ABSTRACT FROM AUTHOR]

Highlights • Different TMS pulse parameters (waveforms and current directions) interact with specific neural cortical components. • The influence of TMS pulse parameters on the efficacy and reliability of TMS measures has not been sufficiently studied. • The results show that waveform/current direction significantly influences the efficacy and reliability of TMS protocols. • Monophasic pulses induce greater and more reliable inhibition in LICI and SICI. • TMS pulses with an anterior–posterior component induce greater ICF, with biphasic pulses resulting in more reliable ICF. Abstract The pulse waveform and current direction of transcranial magnetic stimulation (TMS) influence its interactions with the neural substrate; however, their role in the efficacy and reliability of single- and paired-pulse TMS measures is not fully understood. We investigated how pulse waveform and current direction affect the efficacy and test–retest reliability of navigated, single- and paired-pulse TMS measures. 23 healthy adults (aged 18–35 years) completed two identical TMS sessions, assessing resting motor threshold (RMT), motor-evoked potentials (MEPs), cortical silent period (cSP), short- and long-interval intra-cortical inhibition (SICI and LICI), and intracortical facilitation (ICF) using either monophasic posterior–anterior (mono PA ; n = 9), monophasic anterior–posterior (mono AP ; n = 7), or biphasic (bi AP-PA ; n = 7) pulses. Averages of each TMS measure were compared across the three groups and intraclass correlation coefficients were calculated to assess test–retest reliability. RMT was the lowest and cSP was the longest with bi AP-PA pulses, whereas MEP latency was the shortest with mono PA pulses. SICI and LICI had the largest effect with mono PA pulses, whereas only mono AP and bi AP-PA pulses resulted in significant ICF. MEP amplitude was more reliable with either mono PA or mono AP than with bi AP-PA pulses. LICI was the most reliable with mono AP pulses, whereas ICF was the most reliable with bi AP-PA pulses. Waveform/current direction influenced RMT, MEP latency, cSP, SICI, LICI, and ICF, as well as the reliability of MEP amplitude, LICI, and ICF. These results show the importance of considering TMS pulse parameters for optimizing the efficacy and reliability of TMS neurophysiologic measures. [ABSTRACT FROM AUTHOR]

The application of biomimetic physical stimuli replicating the in vivo dynamic microenvironment is crucial for the in vitro development of functional cardiac tissues. In particular, pulsed electrical stimulation (ES) has been shown to improve the functional properties of in vitro cultured cardiomyocytes. However, commercially available electrical stimulators are expensive and cumbersome devices while customized solutions often allow limited parameter tunability, constraining the investigation of different ES protocols. The goal of this study was to develop a versatile compact electrical stimulator (ELETTRA) for biomimetic cardiac tissue engineering approaches, designed for delivering controlled parallelizable ES at a competitive cost. ELETTRA is based on an open-source micro-controller running custom software and is combinable with different cell/tissue culture set-ups, allowing simultaneously testing different ES patterns on multiple samples. In particular, customized culture chambers were appositely designed and manufactured for investigating the influence of monophasic and biphasic pulsed ES on cardiac cell monolayers. Finite element analysis was performed for characterizing the spatial distributions of the electrical field and the current density within the culture chamber. Performance tests confirmed the accuracy, compliance, and reliability of the ES parameters delivered by ELETTRA. Biological tests were performed on neonatal rat cardiac cells, electrically stimulated for 4 days, by comparing, for the first time, the monophasic waveform (electric field = 5 V/cm) to biphasic waveforms by matching either the absolute value of the electric field variation (biphasic ES at ±2.5 V/cm) or the total delivered charge (biphasic ES at ±5 V/cm). Findings suggested that monophasic ES at 5 V/cm and, particularly, charge-balanced biphasic ES at ±5 V/cm were effective in enhancing electrical functionality of stimulated cardiac cells and in promoting synchronous contraction., Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2023 Gabetti, Sileo, Montrone, Putame, Audenino, Marsano and Massai.)

We have already suggested that there is an active bimodal sphincteric mechanism in the human vesicoureteral junction (VUJ). This mechanism is affected by immaturity, hormonal effects and surgical ablation. This study set out to investigate the effects of anaesthesia on this mechanism. A total of 16 children undergoing surgery were recruited. They were well hydrated. The ureteric jets before and after anaesthesia were recorded using the colour and pulse wave Doppler. Of the total, 14 children showed mature (complex pattern) and two showed immature (monophasic pattern) waveforms before surgery. After anaesthesia, all showed the monophasic waveform (p = 0.01). Thus, the sphincteric action of VUJ as manifest by the complexity of the ureteric jet was modified by anaesthesia by loss of the complex pattern. This supports the hypothesis that the complex pattern is a neural modulation of the simpler myogenic mechanism that produces the monophasic jet. (Email: leuyf2@ctimail.com) [Copyright &y& Elsevier]

Introduction: Lidocaine increases monophasic shock defibrillation energy requirement (DER) values but does not alter biphasic shock DER values. However, the mechanism of this drug/shock waveform interaction is unknown. It may be that lidocaine increases the proarrhythmic actions of monophasic shocks hut not biphasic shocks. Thus, lidocaine may increase monophasic shock DER values by increasing myocardial vulnerability to shock-induced ventricular fibrillation. Methods and Results: Area of myocardial vulnerability (AOV), defined by a two-dimensional grid according to shock strength (y-axis) and shock coupling interval (x-axis), was assessed for biphasic shocks (n = U) and monophasic shocks (n = 13) in intact swine hearts. Shocks were randomly delivered during right ventricular pacing at 10 shock strengths (50 to 500 V) and five coupling intervals (160 to 240 msec). AOV was defined as the number of points within the test grid that induced ventricular fibrillation. AOV, upper limit of vulnerability (ULV), and DER values were determined at baseline and during systemic infusion of lidocaine (10 mg/kg/hour). Lidocaine increased AOV, ULV, and DER values by 35%, 23%, and 36%, respectively, for monophasic shocks. However, lidocaine did not alter AOV, ULV, or DER values for biphasic shocks. Conclusion: Lidocaine increases the AOV to monophasic shocks, which is directly related to changes in ULV and DER values. This implies that lidocaine increases the proarrhythmic activity of monophasic shocks but not biphasic shocks. This may explain why lidocaine increases monophasic shock DER values. [ABSTRACT FROM AUTHOR]

The upper limit of vulnerability (ULV) has been used in clinical studies to predict the DFT in patients with ICDs. Despite the ULV-DFT correlation, uncertainties about the optimal timing of the ULV determination remain. Previous studies using monophasic or bipbasic shock waveforms reported differences in the ULV timing with respect to the electrocardiographic T wave. The purpose of this study was to directly compare the ULV timing for mono- versus biphasic T wave shocks. In ten Isolated rabbit hearts, mono- and biphasic shocks were delivered randomly during the vulnerable window and at varying shock strengths to determine the ULV. the ULV timing was expressed as the coupling interval at the ULV, the myocardial repolarization state at the ULV measured by monophasic action potential recordings, and the relation between the ULV and the peak of the simultaneously recorded volume conducted T wave. The ULV for bipbasic shocks occurred at longer coupling intervals than for monophasic shocks (188.0 ± 9.5 ms vs 173.5 ± 8.8 ms, P < 0.001). This resulted in a more repolarized myocardial state at the ULV for bipbasic than for monophasic shocks (81.1% ± 7.5% vs 66.9% ± 9.0%, P =0.002). The ULV for monophasic shocks occurred predominantly during the upslope of the T wave (8.0 ± 9.7 ms before the peak of the T wave) whereas the ULV for bipbasic shocks occurred at or after the peak of the T wave (5.9 ± 9.3 ms after the peak of the T wave) (P < 0.001). Biphasic shocks delay the timing of the ULV as compared to monophasic shocks. This is important for the prediction of the DFT by ULV measurements. [ABSTRACT FROM AUTHOR]

Electrode polarity has been reported to be one of the factors that affect defibrillation efficacy. We studied the influence of polarity on defibrillation efficacy when monophasic and biphasic waveforms were used with an endocardial lead system. In six anesthetized pigs, defibrillation catheters were placed in the right ventricular (RV) apex and at the junction of the superior vena cava (SVC) and right atrium. Mono phasic shocks were 6 ins in duration, while for biphasic shocks the first phase was 6 ms and the second was 4 ms in duration. Four electrode configurations were tested: R:S, M (the RV electrode, cathode; the SVG electrode, anode, with a monophasic shock); S:R, M; R:S, B (the RV electrode, first phase cathode; the SVC electrode, first phase anode, with a biphasic shock); S:R, B. Defibrillation probability of success curves were determined using an up/down protocol requiring 75 shocks for each configuration. For monophasic shocks, total delivered energy at the 50% probability of success point was significantly lower when the RV electrode was an anode than when it was a cathode (R:S, M: 24.4 ± 7.4 J [mean, ± SD] vs S:R, M: 16.4 ± 5.5 J; P < 0.05). For biphasic shocks, total energy was not affected by polarity reversal of the electrodes (R:S, B: 8.7 ± 1.4 J vs S:R, B: 8.4 ± 2.5 J; P = NS). The endocardial electrode configuration with the RV electrode as an anode requires less energy for defibrillation with a monophasic but not a biphasic waveform. [ABSTRACT FROM AUTHOR]

Introduction: Even though the clinical advantage of biphasic defibrillation waveforms is well documented, the mechanisms that underlie this greater efficacy remain incompletely understood. It is established, though, that the response of relatively refractory cells to the shock is important in determining defibrillation success or failure. We used two computer models of an isolated ventricular cell to test the hypothesis that biphasic stimuli cause a more uniform response than the equivalent monophasic shocks, decreasing the likelihood that fibrillation will he reinduced. Methods and Results: Models of reciprocally polarized and uniformly polarized cells were used. Rapid pacing and elevated [K]o, were simulated, and either 10-msec rectangular monophasic or 5- msec/5-nisec symmetric biphasic .stimuli were delivered in the relative refractory period. The effects of stimulus intensity and coupling interval on response duration and postshock transmembrane potential (Vm) were quantified for each waveform. With reciprocal polarization, biphasic stimuli caused a more uniform response than monophasic stimuli, resulting in fewer large gradients of Vm, (only for shock strengths < 1.25× threshold vs < 2.125< threshold) and a smaller dispersion of repolarization (1611 msec² vs 1835 msec²). The reverse was observed with uniform polarization: monophasic pulses caused a more uniform response than did biphasic stimuli. Conclusion: These results show that the response of relatively refractory cardiac cells to biphasic stimuli is less dependent on the coupling interval and stimulus strength than the response to monophasic stimuli under conditions of reciprocal polarization. Because this may lead to fewer and smaller spatial gradients in Vm, these data support the hypothesis that biphasic defibrillation waveforms will be less likely to reinduce fibrillation. Further, published experimental results correlate to a greater degree with conditions of reciprocal polarization than of uniform polarization, providing indirect evidence that interactions between depolarized and hyper polarized regions play a role in determining the effects of defibrillation shocks on cardiac tissue. [ABSTRACT FROM AUTHOR]

Introduction: This modeling study examines the effect of low-intensity monophasic and biphasic waveforms on the response of a refractory cardiac fiber to the defibrillation shock. Methods and Results: Two cardiac fiber representations are considered in this study: a continuous fiber and a discrete fiber that incorporates gap junctions. Each fiber is undergoing a propagating action potential. Shocks of various strengths and coupling intervals are delivered extracellularly at fiber ends during the relative refractory period. In a continuous fiber, monophasic shock strengths of three times the diastolic threshold either elicit no response or, for coupling intervals above 380 msec, reinitiate propagation. In contrast, biphasic shocks of same strength are capable of terminating the existing wavefronts by either invoking a non-propagating response (coupling intervals 370 to 382 msec) that prolongs the refractory period or inducing wavefront collision (coupling intervals above 400 msec). The fiber response is similar for other shock strengths and when cellular discontinuity is accounted for. Thus, for a refractory fiber, biphasic shocks have only a small "vulnerable" window of coupling intervals over which propagation is reinitiated. Conclusion: At short coupling intervals, a significant extension of refractoriness is generated at regions where the biphasic shock induced hyperpolarization followed by depolarization. At large coupling intervals, the enhanced efficacy of biphasic shocks is associated with their ability to induce wavefront collision, thus decreasing the probability of reinitiating fibrillation. Overall, the defibrillation shock affects the tissue through the induced large-scale hyperpolarization and depolarization, and not through the small-scale transmembrane potential oscillations at cell ends. [ABSTRACT FROM AUTHOR]

Field-Induced Excitatory Responses Across Propagating Waves. Introduction: Biphasic (BP) defibrillation waveforms have been shown to be significantly more efficacious than equivalent monophasic (MP) waveforms. However, when defibrillation falls, it tends to do so first in distal rejection of the heart where induced field gradient magnitudes are lowest. We tested the hypothesis that the improved efficacy of BP waveforms results from their enhanced ability to prevent the initiation of new postshock activation fronts behind preexisting; wavetails, rather than from any significantly improved ability to terminate preexisting wavefronts. Methods and Results: An idealized computer model of a one-dimensional cardiac strand was used to investigate the spatial and temporal interactions between an underlying propagation front (or tail) and uniform MP or BP field stimuli of various intensities. Axial discontinuities from intercellular junctions induced sawtooth patterns of polarization during such field stimuli, enabling the shocks to interact directly with all cells. MP and BP diastolic thresholds were essentially equal. All suprathreshold MP and BP field stimuli successfully terminated preexisting wavefronts by directly depolarizing tissue ahead of those fronts, thus blocking their continued progression. However, the postshock response at the wavetail was significantly dependent on the shape and strength of the administered field. Low-strength MP stimuli induced an all-or-none excitation response across the wavetail, producing a sharp spatial transmembrane voltage gradient from which a new sustained anterogradely propagating wavefront was initiated. In contrast, low-strength BP field stimuli induced a spatially graded excitatory response whose voltage gradient was insufficient to initiate such a wavefront. Higher-strength MP and BP stimuli both produced graded excitatory responses with no subsequent propagation. Conclusions: Shock-induced spatial "all-or-none" excitatory responses facilitate, and graded excitatory responses prevent, the postshock initiation of new propagating wavefronts. Moreover, BP field stimuli can induce such graded excitatory responses at significantly lower stimulus strengths than otherwise equivalent MP stimuli. Therefore, these results support an alternative "graded excitatory response" mechanism for the improved efficacy of BP over MP field stimuli in low gradient regions. [ABSTRACT FROM AUTHOR]

Introduction: The reason for the increased defibrillation efficacy of biphasic shocks over monophasic shock is not definitely known. Methods and Results: In six anesthetized pigs, we mapped the epicardium after transvenous defibrillation shocks to compare the activation patterns following successful biphasic shocks with unsuccessful monophasic shocks of the same voltage. The heart was exposed and a 510-electrode sock with approximately 4-mm interelectrode spacing was pulled over the entire ventricular epicardium and sutured to the pericardium. Defibrillation catheters were placed in the right ventricular apex and in the superior vena cava. Paired monophasic 12 msec and biphasic 6/6 msec defibrillation shocks were given using an up-down protocol to keep shock strength between the defibrillation thresholds for the two waveforms so that the biphasic shock was successful while the monophasic shock was not. Activation fronts immediately following 60 paired shocks were recorded and analyzed by animated maps of the first derivative of the electrograms. The ventricles were divided into apical (I), middle (II), and basal (III) thirds, and early sites, i.e., the sites from which activation fronts first appeared on the epicardium following the shock, were grouped according to their location. Postshock intervals, i.e., the time from the shock until earliest epicardial activation occurred, were also determined. No ectopic activation fronts followed the shock in 20 biphasic episodes. In the other 40 paired episodes, the number of early sites was smaller after biphasic shocks than after monophasic shocks (monophasic: 198 (total), 3.3 ± 0.9 (mean ± SD) per shock episode; biphasic: 67, 1.1 ± 1.0, P < 0.05]. For biphasic but not monophasic shocks, early sites were less likely to arise from the middle (11) and basal (III) thirds than from the apical third (I) [monophasic: I: 84 (42%), II: 68 (34%), III: 46 (23%); biphasic: I: 49 (73%), II: 10 (15%), III: 8 (12%), P < 0.05]. Postshock intervals were significantly shorter for monophasic shocks (54 ± 14 msec) than for biphasic shocks (75 ± 23 msec, P < 0.05). Conclusion: The decreased number of activation fronts and the longer delay following the shock for the earliest epicardial appearance of those activation fronts that do occur may be responsible for the increased defibrillation efficacy for biphasic shocks. [ABSTRACT FROM AUTHOR]