Wave Transit Time Research Articles

Un nouvel index pour évaluer le vieillissement artériel indépendamment de la pression artérielle : pOpscore®

AimPulse wave velocity does not correlate to age in the upper limb but in the aorta and lower limb. We studied the link between ageing and pulse wave transit time (PWtt) indexes at the toe and finger. Patients and methodsMeasurements were performed in 300 patients in occupational medicine and primary care after 5minutes supine rest using the device studied (pOpmètre®, Axelife SAS, France). It measures transit time between R-ECG and finger or toe pulse signal (ttf or ttt respectively). We define as follows three indexes: difference between transit times: Dtf=ttt−ttf; pulse wave velocity PWVft=k*subjects height/Dtf (m/s); and the pOpscore® as the ratio of toe PWV/fingerPWV. ResultsOf the 300 tested patients, 147 were analysed using univariate correlation: age (P<10−4), SBP (P<10−4), DBP (P<0.02) and BMI (P<0.04) correlated to Dtf, PWVtf and pOpscore®. Using stepwise regression analysis with Age, BMI, SBP, DBP, MBP: Dtf was dependent with age (P<10−4) and SBP (P<0.01); PWVtf with age (P<0.0001), SBP (P<0.01) and DBP (P<0.05); pOpscore® was dependent only to age (P<10−4). ConclusionIn this study, in contrast with the other vascular indexes studied dependent to age and blood pressure, pOpscore® was dependent only to ageing. pOpmètre® is a promising technique for routine determination of arterial stiffness and pOpscore® appears to be appropriate to study the structural vascular ageing in outpatient.

Correlation of blood pressure, obesity, and adherence to the Mediterranean diet with indices of arterial stiffness in children

The aim of the study was to assess the hypothesis that obesity, blood pressure (BP), and dietary habits (adherence to the Mediterranean diet) are related to indices of arterial stiffness (AS) in childhood. Two hundred and seventy-seven children aged 12 years were measured with the R6.5 Pulsecor® monitor, which performs measurements using an upper arm BP cuff held at above systolic pressure for a short time. The augmentation index (AI) in the brachial artery, the peripheral pulse pressure to central pulse pressure (PPP/CPP) ratio, and the reflected wave transit time to height ratio were used as indices of AS. The degree of adherence to the Mediterranean diet was assessed by the KIDMED index which includes 16 questions on specific dietary habits. Forty-three percent of the children were overweight and obese. Overweight and obese children had significantly lower PPP/CPP and KIDMED score in comparison to children with normal body mass index (BMI). In multivariate regression models, indices of AS were related to mean peripheral BP, heart rate, and height, while BMI had an independent correlation to PPP/CPP. The KIDMED index also had a negative correlation with AI independently of obesity. Obesity and adherence to the Mediterranean diet patterns are factors related independently to indices of AS even in 12-year-old children.

Effects of olmesartan on arterial stiffness in rats with chronic renal failure

BackgroundIt has been suggested that the antioxidant properties of olmesartan (OLM), an angiotensin II type 1 receptor (AT1R) blocker, contribute to renal protection rather than blood pressure lowering effects despite the fact that causal relationships between hypertension and renal artery disease exist. This study aimed to examine the hypothesis whether the antioxidative activities of OLM were correlated to arterial stiffness, reactive oxygen species and advanced glycation end products (AGEs) formation in rats with chronic renal failure (CRF).MethodsCRF rats were induced by 5/6 nephrectomy and randomly assigned to an OLM (10 mg/day) group or a control group. Hemodynamic states, oxidative stress, renal function and AGEs were measured after 8 weeks of OLM treatment.ResultsAll the hemodynamic derangements associated with renal and cardiovascular dysfunctions were abrogated in CRF rats receiving OLM. Decreased cardiac output was normalized compared to control (p <0.05). Mean aortic pressure, total peripheral resistance and left ventricular weight/body weight ratio were reduced by 21.6% (p <0.05), 28.2% (p <0.05) and 27.2% ((p <0.05). OLM also showed beneficial effects on the oscillatory components of the ventricular after-load, including 39% reduction in aortic characteristic impedance (p < 0.05), 75.3% increase in aortic compliance (p <0.05) and 50.3% increase in wave transit time (p < 0.05). These results implied that OLM attenuated the increased systolic load of the left ventricle and prevented cardiac hypertrophy in CRF rats. Improved renal function was also reflected by increases in the clearances of BUN (28.7%) and serum creatinine (SCr, 38.8%). In addition to these functional improvements, OLM specifically reduced the levels of malondialdehyde (MDA) equivalents in aorta and serum by 14.3% and 25.1%, as well as the amount of AGEs in the aortic wall by 32% (p < 0.05) of CRF rats.ConclusionOLM treatment could ameliorate arterial stiffness in CRF rats with concomitant inhibition of MDA and AGEs levels through the reduction of oxidative stress in aortic wall.

P-004 PULSE PRESSURE AMPLIFICATION OVER UPPER ARM

Objectives We decomposed the lower body and upper limb reflections from the brachial PW to quantify their relative contributions to the aorta-to-brachial Pulse pressure amplification (PPA). Background PPA between central aorta and brachial artery is affected by wave reflections from both lower body and local upper limb. Methods High fidelity central aortic and right brachial PWs were simultaneously recorded at baseline and 3 minutes after sublingual nitroglycerin (NTG) administration, using a custom-made dual pressure sensor catheter in 54 patients (66.2 ± 13.0 year; 45 men). Lower body reflected PW (amplitude = Pb) was decomposed from the aortic PW. Local upper limb reflected PW (amplitude = P0) was obtained by subtraction of the aortic PW from the foot-aligned brachial PW. Aorta-to-brachial pulse wave velocity (abPWV) was calculated from the simultaneously recorded aortic and brachial PWs. Results PPA was 5.4 ± 5.9 mmHg and increased to 10.9 ± 6.1 mmHg after NTG. Pb decreased by 39.6 ± 18.7 % and P0 by 6.7 ± 29.0 % after NTG. By forward multivariate linear regression analysis, the total variance (r2 = 0.76) of PPA could be explained by P0 (54.9%), Pb (33.0%), total arterial compliance (5.7%), abPWV (3.4%), and reflected wave transit time (3.0%), whereas the total variance (r2 = 0.53) of P0 could be explained by abPWV (57.3%), Pb (37.2%), and heart rate (5.5%). Conclusions Local wave reflection contributes substantially to the aorta-to-brachial PPA, an emerging mechanical biomarker of cardiovascular risk.

Changes in some indices of the cardiovascular system in different mental tasks

In order to study the effects of the type of mental activity on the function of the cardiovascular system in humans, the following indices were used: the heart rate (HR), RR interval, variation magnitude (VM), systolic wave amplitude (SWA), and pulse wave transit time (PWTT). These indices were recorded when the subjects solved verbal-logical or spatial mental tasks. The HR was substantially increased during solving of the spatial tasks as compared to solving of the verbal-logical tasks, whereas the SWA showed the opposite changes. The latencies of the performance of the tasks of various types were similar in the subjects; therefore, the changes in the autonomic indices did not depend on the difficulties of the mental tasks. They rather depended on specific features of the mental processes involved in the performance of the tasks of different types. Thus, changes in the HR and the decreased SWA, which was related to elevated blood pressure, represent the effect of the sympathetic nervous system on the heart function during solving verbal-logical tasks. Our data demonstrate that the HR and blood pressure can be used as additional indices for the development of new techniques for assessment of different types of mental processes together with the indices of electrical brain activity.

Detection of delamination in concrete using ultrasonic pulse velocity test

An experimental study was performed to evaluate the delamination in the concrete using ultrasonic pulse velocity (UPV) method. Two slab specimens of 150-mm and 300-mm thicknesses consisted of delaminations of varying sizes at quarter depths. Using indirect transmission method, the transit times of longitudinal and Rayleigh waves were measured to determine the dynamic Young’s modulus and Poisson’s ratio of the concrete. The static modulus was also measured and compared. The location and size of the delaminations in the slab were evaluated from the direct transmission method. The diffraction of the longitudinal wave at delaminations decreased the wave velocity and a qualitative correlation was established between the transit time of the UPV signal and the size of the delamination.

Non-invasive estimation of stroke volume index by using pulse wave transit time both in adult and pediatric population

Non-invasive estimation of stroke volume index by using pulse wave transit time both in adult and pediatric population

Gender differences in the extent and timing of the reflected arterial waveform in the presence of coronary artery disease

The non-invasive assessment of arterial dysfunction may improve cardiovascular (CV) risk assessment. We studied the relationship of the reflected wave transit time (RWT) and augmentation index (AIX), both derived from pulse wave analysis (PWA), in the presence/absence of coronary artery disease (CAD), and compared PWA with the ankle-brachial index (ABI). A trained research nurse measured PWA (radial applanation tonometry, SphygmoCor device) and ABI (hand-held Doppler) in a consecutive series of fasted patients resting supine prior to elective coronary angiography. Measurements were undertaken blind to other clinical information. Mean differences in RWT, AIX, and ABI in the presence of CAD were adjusted for age, height, mean BP, fasting cholesterol, ever smoked, and treated hypertension using multiple linear regression. We recruited 125 patients (49 women) with a mean age of 65 years, total cholesterol 4.4 mmol/l, BP 136/78, current smokers 22%, and previous myocardial infraction 30%. A statistically significant interaction between sex and CAD was present for both RWT (p = 0.003) and AIX (p = 0.03). No interaction was demonstrated for ABI (p = 0.21). Mean differences for men and women in the presence/absence of CAD were: RWT -10.1 vs. +5.2 milliseconds; AIX +1.2 vs. -5.4; ABI -0.02 vs. -0.10. Male and female area under receiver operating characteristic curves for CAD detection differed for RWT (0.33 vs. 0.67) and AIX (0.62 vs. 0.36), but were similar for ABI (0.40 vs. 0.34). The timing and extent of arterial wave reflections in the presence of CAD may differ in men and women.

Relationship between arterial dysfunction and extra-articular features in patients with rheumatoid arthritis

Systemic inflammation may be a common process that underpins both atherosclerosis and extra-articular features (ExRA) of rheumatoid arthritis (RA). We evaluated the relationship between ExRA and arterial dysfunction in 114 consecutive patients with RA (82% women) without overt arterial disease aged 40-65years. A trained research nurse undertook 'SphygmoCor' pulse wave analysis (PWA) using radial applanation tonometry to measure the extent (augmentation index, AIX%) and timing (reflected wave transit time, RWT, msec) of aortic wave reflection. Assessment included fasting blood sample, patient questionnaire and medical record review. Mean differences were adjusted for age, sex, mean blood pressure, smoking pack-years, fasting cholesterol, Stanford HAQ score and erythrocyte sedimentation rate. Mean age was 54 (SD 7) and median RA duration 10 (IQR 4-17) years. There was a trend for arterial dysfunction (higher AIX%; lower RWT) to increase as the number of ExRA features rose, but no difference in AIX% (-0.5, 95%CI -2.8 to 1.8, P=0.65) or RWT (0.3ms, 95%CI -3.6 to 4.2, P=0.86) between 'any ExRA' and 'no ExRA'. Arterial dysfunction was not associated with the presence of rheumatoid nodules, Sjogren's syndrome or carpal tunnel syndrome. Our study was too small to determine whether severe ('Malmo') ExRA (vasculitis, pericarditis, episcleritis) was truly associated with a higher AIX% (3.8, 95%CI -2.3 to 9.9, P=0.22) and lower RWT (-5.5ms 95%CI -13.1 to 2.1, P=0.16). While arterial dysfunction may be associated with the number of ExRA features and severe ExRA, it does not appear to be associated with other ExRA features.

The Characteristics of Ultrasonic Wave Transmitted Through Drying Wood

The possibility of using the properties of an ultrasonic wave as a means for monitoring the moisture content of a board during drying was investigated. The ultrasonic wave signals are influenced by moisture content and other factors such as temperature, moisture gradient and coupling area. The effect of temperature was examined by measuring the transit times, amplitudes and velocities of ultrasonic waves transmitted through air, a metal bar and a board at various temperatures. The effect of a moisture gradient was studied using a model specimen composing five wood pieces of various moisture contents. The velocity and amplitude of the ultrasonic waves transmitted through air increase with temperature, while those through a metal bar and a board decrease. It was confirmed that the temperature effect is partially attributed to the change of transducer's properties. The effect of a moisture gradient on the velocity of an ultrasonic wave varies with the average moisture content of a board. As the dimension of the end face of a board increases the velocity of an ultrasonic wave increases and low frequency components more dominates than high frequency components. The transit times of ultrasonic waves transmitted through a board during kiln drying reflect the temperature steps in the drying schedule and the transducer temperatures.

Pyridoxamine prevents age-related aortic stiffening and vascular resistance in association with reduced collagen glycation

An increase in oxidative chemical modifications of tissue proteins by advanced glycation end products (AGEs) and advanced lipoxidation end products (ALEs) has been implicated in normal aging. Pyridoxamine (PM), one of the three natural forms of vitamin B 6, has been identified as an inhibitor of AGE/ALE products formed during the autoxidation of carbohydrates and peroxidation of lipids. The current study seeks to determine whether PM intervention could prevent the age-related aortic stiffening and vascular resistance through its ability to inhibit the pathogenic cross-linking of glycated collagen. Male Fisher 344 rats at 15 months were treated daily with PM (1 g l − 1 in drinking water) for 5 months and compared with the age-matched, untreated controls at 20 months. Pulsatile aortic pressure and flow signals were measured to perform the vascular impedance analysis. The anti-AGE antibody 6D12 was used to detect glycation-derived modification of aortic collagen, using protein blotting analysis. PM therapy attenuated the age-related increase in total peripheral resistance. An increase in wave transit time and aortic compliance by PM indicated that the drug improved aortic distensibility of the aged vasculature. This paralleled its reduction of AGE-collagen cross-links on aortas. Treatment of the old animals with PM also prevented the age-induced augmentation in vascular load imposed on the heart, as evidenced by an increased wave transit time and a decreased wave reflection factor. These findings suggest a partial role of PM in improving arterial mechanics by targeting the pathogenic formation of AGE-induced aortic collagen cross-links in old rats.

Central aortic blood pressure, augmentation index, and reflected wave transit time: reproducibility and repeatability of data obtained by oscillometry

BackgroundThe evidence suggests that arterial stiffness acts as an independent predictor of general as well as cardiovascular mortality, strokes in patients with arterial hypertension, type 2 diabetes mellitus in the elderly, and in the general population. The oscillometric method measures parameters of arterial stiffness by applying special methods of processing oscillograms. This is a study of the reproducibility and repeatability of central aortic systolic blood pressure (SBP), augmentation index, and reflected wave transit time measured by Vasotens® technology.MethodsAnthropometric and hemodynamic measurements for 90 volunteers were made by two observers using the 24-hour blood pressure monitoring system, BPLab®, with Vasotens technology in “office” mode, over a period of two days and always at the same time in the morning. Initialization of the device was performed prior to each measurement cycle for each participant.ResultsAnalysis of short-term repeatability and reproducibility data for central aortic systolic blood pressure, reflected wave transit time, and augmentation index did not reveal any statistically significant differences. For observer A, SBP was 0.11 ± 7.53 mmHg and aortic SBP was 0.26 ± 6.11 mmHg; for observer B, SBP was 0.14 ± 8.42 and aortic SBP was 0.2 ± 7.25 mmHg. Short-term reproducibility for the different observers with averaging of both measurements was 0.36 ± 5.69 mmHg for SBP and 0.37 ± 6.7 mmHg for aortic SBP; the next day, repeatability for observer A was 0.52 ± 10.7 mmHg for SBP and 0.73 ± 8.98 mmHg for aortic SBP.ConclusionBPLab with Vasotens technology has good reproducibility and repeatability, and can be recommended for clinical vascular risk estimation.

Non-steroidal anti-inflammatory drug (NSAID) related inhibition of aldosterone glucuronidation and arterial dysfunction in patients with rheumatoid arthritis: a cross-sectional clinical study

ObjectivePatients with rheumatoid arthritis (RA) are at increased risk of cardiovascular (CV) disease and are also commonly prescribed non-selective non-steroidal anti-inflammatory drugs (ns-NSAIDs). New in vitro evidence suggests that this...

Determinants of pressure wave reflection: characterization by the transit time-independent reflected wave amplitude

The effects of pressure wave reflection have been incompletely described by the central augmentation index (cAI) and augmented pressure (Pa). We therefore investigated the determinants of amplitude of the reflected wave (Pb), which is independent of the reflected wave transit time (RWTT) and has been shown to predict cardiovascular mortality in the general population. A total of 180 (117 men, mean age 68 years old) patients were recruited. Carotid pressure waveforms derived by tonometry at baseline and 3 min after administration of sublingual nitroglycerin (NTG) were calibrated and then decomposed into the forward and backward waves to yield Pb. The ratio of pre-ejection period/ejection time (PEP/ET) was measured. By stepwise multivariate analysis, independent determinants of Pb included brachial mean blood pressure (β=0.56, P<0.001), heart rate (β=-0.29, P<0.001), age (β=0.20, P<0.001), PEP/ET (β=-0.16, P=0.004) and height (β=-0.13, P=0.018). RWTT, body mass index and sex were significant independent determinants of Pa and cAI but did not contribute to Pb. Change of Pb but not Pa or cAI significantly predicted the changes of carotid systolic (r=0.550, P<0.001) and pulse pressure (r=0.618, P<0.001) after NTG. In conclusion, determinants of Pb differ from those of cAI and Pa. Pb is independent of sex and RWTT.

Time of flight analysis of pulsating aurora electrons, considering wave‐particle interactions with propagating whistler mode waves

We propose a model for the energy dispersion of electron precipitation associated with pulsating auroras, considering the wave‐particle interactions with propagating whistler mode waves from the equator. Since the resonant energy depends on the magnetic latitude, the pitch angle scattering of different energy electrons can occur continuously along the field line. Considering the energy‐dependent path length and the precipitation start time of the precipitating electrons, the transit time of whistler mode waves, and the frequency drift, we calculated the precipitation of electrons observed at the topside ionosphere. Note that higher energy electrons precipitate into the ionosphere of the opposite hemisphere earlier than lower energy electrons. As a result, an energy dispersion of precipitating electrons is observed at the topside ionosphere, even though the modulation of low energy electrons occurs prior to that of high energy electrons. Using the model, we conducted a time‐of‐flight (TOF) analysis of precipitating electrons observed by the REIMEI satellite, assuming an interaction with the whistler mode chorus rising tone. Our TOF analysis suggests that the modulation region of the pitch angle scattering is near the magnetic equator, whereas previous models expected that the modulation region is far from the magnetic equator. The estimated parameters, such as wave‐frequency and latitudinal distribution of the modulation region, are consistent with previous statistical studies of whistler waves at the magnetosphere.

Distal Shift of Arterial Pressure Wave Reflection Sites With Aging

An early return of reflected waves, the backward propagation of the arterial pressure wave from the periphery to the heart, is associated with the augmentation of central pulse pressure and cardiovascular risks. The locations of arterial pressure wave reflection, along with arterial stiffening, have a major influence on the timing of the reflected wave. To determine the influence of aging on the location of a major reflection site, arterial length (via 3D artery tracing of MRI) and central (carotid-femoral) and peripheral (femoral-ankle) pulse wave velocities were measured in 208 adults varying in age. The major reflection site was detected by carotid-femoral pulse wave velocity and the reflected wave transit time (via carotid arterial pressure wave analysis). The length from the aortic valve to the major reflection site (eg, effective reflecting length) significantly increased with aging. The effective reflecting length normalized by the arterial length demonstrated that the major reflection sites were located between the aortic bifurcation and femoral site in most of the subjects. The normalized effective reflecting length did not alter with aging until 65 years of age and increased remarkably thereafter in men and women. The effective reflecting length was significantly and positively associated with the difference between central and peripheral pulse wave velocities (r=0.76). This correlation remained significant even when the influence of aortic pulse wave velocity was partial out (r=0.35). These results suggest that the major reflection site shifts distally with aging partly because of the closer matching of impedance provided by central and peripheral arterial stiffness.

Numerical simulation of elastic waves for visualization of defects

Due to aging of civil infrastructure, non-destructive testing (NDT) is of continuously increasing significance. The ultimate aim is the detection of defects in the interior of a structure with the highest possible accuracy, in order to proceed to specific repair action. Pulse velocity tomography is a technique to visualize the interior. Using a number of pulsers and receivers for introduction and recording of the transient elastic wave at different points on the surface of a structure, a potentially dense network of interconnecting wave paths are examined as to their wave transit time. Each “cell” of the cross section is assigned a velocity value and the interior is visualized. However, the confirmation of the results is not always possible except for cases where the cracks are visible from the surface or in case specific model defects are placed during casting of specimens. In the present paper numerical simulations of wave propagation were conducted for different geometries. Different types of inhomogeneity were applied, such as voids, deteriorated zones, as well as steel reinforcing bars. The transit time information calculated in these cases, led to the corresponding tomograms. Based on the comparison between the actual geometry of the void and the tomograms, the accuracy of the technique is studied, as well as parameters to improve the testing, like applied excitation frequency and number of sensors.

Relationship Between Urinary Salt Excretion and Pulse Pressure and Central Aortic Hemodynamics Independent of Steady State Pressure in the General Population

Although central pulse pressure (PPc) is strongly related to central mean arterial pressure (MAPc), PPc predicts cardiovascular outcomes beyond MAPc. Whether modifiable risk factors for hypertension contribute to PPc and its determinants, independent of MAPc, is uncertain. In 635 randomly recruited participants, we assessed the independent relationship between 24-hour urinary sodium (Na(+)) or potassium (K(+)) excretion and brachial artery PP (in office or 24-hour; n = 487), PPc, the forward (P1) and augmented (Paug) pressure wave components of PPc, central augmentation index, and determinants of central pressure waves, including aortic pulse wave velocity, effective reflecting distance, and reflective wave transit time. Central dynamics were determined using applanation tonometry of the carotid, femoral, and radial arteries. With adjustments for potential confounders, urinary Na(+)/K(+) was independently associated with in-office, central, and 24-hour PP, as well as Paug, P1, and central augmentation index (P<0.05 to P<0.005). With further adjustments for MAPc (or diastolic BP), urinary Na(+)/K(+) was independently associated with PPc, 24-hour PP, Paug, P1, and central augmentation index (P<0.05 to P = 0.005) but not with in-office PP, pulse wave velocity, effective reflecting distance, or reflective wave transit time. In conclusion, in a population of African ancestry, urinary salt excretion is independently related to central and 24-hour PP independent of MAPc or diastolic BP, effects that are attributed to increases in both P1 and Paug but not to pulse wave velocity. Hence, modifying salt intake could influence cardiovascular risk through effects on 24-hour and central PPs, as well as P1 and Paug, independent of steady-state pressure (MAP or diastolic BP) or pulse wave velocity.

Effects of acetyl‐L‐carnitine and oxfenicine on aorta stiffness in diabetic rats

We compared the haemodynamic and metabolic effects of acetyl-L-carnitine (one of the carnitine derivatives) and of oxfenicine (a carnitine palmitoyltransferase-1 inhibitor) in streptozotocin-induced diabetes in male Wistar rats. Diabetes was induced by a single tail vein injection of 55mgkg(-1) streptozotocin. The diabetic animals daily treated with either acetyl-L-carnitine (150mgkg(-1) in drinking water) or oxfenicine (150mgkg(-1) by oral gavage) for 8weeks,were compared with the untreated age-matched diabetic controls. Arterial wave reflection was derived using the impulse response function of the filtered aortic input impedance spectra. Thiobarbituric acid reactive substances (TBARS) measurement was used to estimate malondialdehyde (MDA) content. Oxfenicine, but not acetyl-L-carnitine, increased total peripheral resistance in diabetes, which paralleled its elevation in plasma levels of free fatty acids. By contrast, acetyl-L-carnitine, but not oxfenicine, resulted in a significant increase in wave transit time and a decrease in wave reflection factor, suggesting that acetyl-L-carnitine may attenuate the diabetes-induced deterioration in systolic loading condition for the left ventricle. This was in parallel with its lowering of MDA/TBARS content in plasma and aortic walls in diabetes. Acetyl-L-carnitine therapy also prevented the diabetes-related cardiac hypertrophy, as evidenced by the reduction in ratio of the left ventricular weight to body weight. Acetyl-L-carnitine, but not oxfenicine, attenuates aortic stiffening and cardiac hypertrophy, possibly through its decrease of lipid oxidation-derived MDA/TBARS in the rats with insulin deficiency.

Improving the output voltage waveform of an intense electron-beam accelerator based on helical type Blumlein pulse forming line

The Blumlein pulse forming line (BPFL) consisting of an inner coaxial pulse forming line (PFL) and an outer coaxial PFL is widely used in the field of pulsed power, especially for intense electron-beam accelerators (IEBA). The output voltage waveform determines the quality and characteristics of the output beam current of the IEBA. Comparing with the conventional BPFL, an IEBA based on a helical type BPFL can increase the duration of the output voltage in the same geometrical volume. However, for the helical type BPFL, the voltage waveform on a matched load may be distorted which influences the electron-beam quality. In this paper, an IEBA based on helical type BPFL is studied theoretically. Based on telegrapher equations of the BPFL, a formula for the output voltage of IEBA is obtained when the transition section is taken into account, where the transition section is between the middle cylinder of BPFL and the load. From the theoretical analysis, it is found that the wave impedance and transit time of the transition section influence considerably the main pulse voltage waveform at the load, a step is formed in front of the main pulse, and a sharp spike is also formed at the end of the main pulse. In order to get a well-shaped square waveform at the load and to improve the electron-beam quality of such an accelerator, the wave impedance of the transition section should be equal to that of the inner PFL of helical type BPFL and the transit time of the transition section should be designed as short as possible. Experiments performed on an IEBA with the helical type BPFL show reasonable agreement with theoretical analysis.