Effective reduction of scatter radiation for operator and assistant during coronary procedures with a suspended radiation protection system in a per-procedure live-dosimetry analysis

Background

Interventional cardiologists (IC) are exposed to the highest doses of radiation compared to all other medical specialties. Although head and eyes are exposed to a significant dose of scatter radiation (SCR), precise per-procedure data is sparse. Recently, the EU guidelines for maximum eye lens SCR doses have been reduced from 150 mSv to 20 mSv per year. A ceiling suspended operator radiation protection system has shown additional benefits for SCR protection in radiologic interventional procedures.

Purpose

To study the impact of the ZG system on IC and sterile assistant (SA) SCR exposure when used in addition to the current standard of X-ray protection (SXP) in unselected all-comers cardiologic procedures.

Methods

IC and SA were equipped with Unfors RaySafe i3 live-dosimeters at prespecified locations. 181 consecutive cardiac procedures were recorded, in which either both IC and SA were using SXP (lead apron, thyroid shield) or the IC was using the ZG system and the SA was wearing SXP. In all procedures a suspended lead shield, patient lead cover and an adjustable lead side-shield were present. Diagnostic angiographies (DA) and interventions (PCI) were grouped separately. Within both groups, the IC's and SA's SCR doses were compared.

Results

SCR doses were recorded in 100 DA and 81 PCI procedures. Compared to SXP, the use of the ZG device reduced the average SCR doses per procedure of the IC recorded at the left lateral head from 5.18±1.11 μSv to 0.60±0.07 μSv in DA (−88%; n=49/49, p<0.0001) and from 19.64±3.36 μSv to 1.05±0.28 μSv for PCI (−95%; n=54/23, p=0.0006). The IC's average frontal dose at eye level was reduced from 1.38±0.33 μSv to 0.36±0.04 μSv in DA (−74%; n=50/50, p=0.0033) and from 3.33±0.53 μSv to 0.88±0.20 μSv in PCI (−74%; n=55/25, p=0.0031). Consistently, the dose recorded immediately under the IC's left shoulder were reduced from 34.14±7.79 μSv to 1.59±0.32 μSv in DA (−95%; n=39/40, p=0.0001) and from 71.77±10.77 μSv to 3.95±0.83 μSv in PCI (−94%; n=44/23, p=0.0001). Furthermore, when the IC used the ZG system, the average SCR dose recorded at the SA's head was reduced from 4.32±0.98 μSv to 2.11±0.28 μSv in DA (−51%, n=45/49, p=0.027) and from 18.55±2.69 μSv to 6.93±1.93 μSv in PCI (−63%, n=54/24, p=0.0078). With the exception of the IC frontal dose, all SCR dose effects remained significant after correction for total radiation time (μSv/s) and dose-area product (μSv/Gy·cm2). Procedure duration, contrast use and patient radiation dose were not affected by ZG use.

Conclusions

In a representative all-comers cohort of cardiac procedures, the ZG X-ray protection system demonstrated an impressive potential for SCR reduction in critical anatomical areas - even in a state-of-the-art cath-lab inventory with multiple SCR reduction measures already in place. Remarkably, the protective effect also included the sterile assistant at the table wearing SXP.

Funding Acknowledgement

Type of funding sources: None.

Safe application of extensive radiotherapy to a cardiac resynchronization device

Patients with cardiac implantable electronic devices undergoing radiotherapy (RT) are prone to the risk of device failure. Guidelines and manufacturer's instructions are lacking practical recommendations for cumulative radiation doses to pacemakers or implantable cardioverter defibrillators. The present case demonstrates the effect of RT of a Merkel cell carcinoma near the location of a cardiac resynchronization therapy pacemaker. Despite guideline recommendations, surgical relocation or de novo implantation of the device on the contralateral side was avoided to prevent the dissemination of tumour cells, inflammation, and wound healing complications. A total dose of 47.25 Gy applied in very close proximity to the cardiac resynchronization therapy pacemaker was carried out safely without jeopardizing the patient and any device malfunction during and after treatment within >1.5 years of follow‐up period. The present case demonstrates that high‐dose RT near to a cardiac resynchronization therapy device can be carried out safely. Special precautions during RT as well as close device follow‐up interrogations are mandatory. Large‐scale studies are needed for the true frequency of adverse events.

Minimally invasive system for baroreflex activation therapy chronically lowers blood pressure with pacemaker-like safety profile: results from the Barostim neo trial

BACKGROUND

Previous trials have demonstrated clinically significant and durable reductions in arterial pressure from baroreflex activation therapy (BAT), resulting from electrical stimulation of the carotid sinus using a novel implantable device. A second-generation system for delivering BAT, the Barostim neo™ system, has been designed to deliver BAT with a simpler device and implant procedure.

METHODS

BAT, delivered with the advanced system, was evaluated in a single-arm, open-label study of patients with resistant hypertension, defined as resting systolic blood pressure (SBP) ≥140 mm Hg despite treatment with ≥3 medications, including ≥1 diuretic. Stable medical therapy was required for ≥4 weeks before establishing pretreatment baseline by averaging two SBP readings taken ≥24 hours apart.

RESULTS

Thirty patients enrolled from seven centers in Europe and Canada. From a baseline of 171.7 ± 20.2/99.5 ± 13.9 mm Hg, arterial pressure decreased by 26.0 ± 4.4/12.4 ± 2.5 mm Hg at 6 months. In a subset (n = 6) of patients with prior renal nerve ablation, arterial pressure decreased by 22.3 ± 9.8 mm Hg. Background medical therapy for hypertension was unchanged during follow-up. Three minor procedure-related complications occurred within 30 days of implant. All complications resolved without sequelae.

CONCLUSION

BAT delivered with the second-generation system significantly lowers blood pressure in resistant hypertension with stable, intensive background medical therapy, consistent with studies of the first-generation system for electrical activation of the baroreflex, and provides a safety profile comparable to a pacemaker.

[Renal sympathetic denervation. A novel interventional treatment option for therapy-resistant arterial hypertension]

As much as one third of patients with arterial hypertension are treatment refractory as they do not reach sufficient blood pressure control despite antihypertensive combination therapy of significant duration. In patients with therapy-resistant hypertension, the kidneys play a central role as activator of the sympathetic nervous system. Sympathetic nervous activation via efferent nerve fibers lying in the adventitia of the renal arteries leads to increased Na(+) reabsorption, increased renin secretion and reduction of renal plasma flow. Via afferent sympathetic fibers in the dorsal root of the spinal chord, the kidneys induce a further augmentation of central sympathetic nervous activity. With the method of renal sympathetic denervation (RSD) an interventional minimally invasive procedure has become available to precisely ablate afferent and efferent sympathetic nervous fibers surrounding the renal artery. Via an ablation catheter with an electrode tip and a radiofrequency generator a series of 4-6 ablation sites are administered in both renal arteries leading to denervation of the sympathetic nerve fibers while keeping the renal artery intact. Recent studies showed a significant and continuous reduction of blood pressure of 25-30 mmHg systolic and 10-15 mmHg diastolic for at least 2 years. Concerning the role of elevated sympathetic nervous system activity in forms of hypertension associated with other disorders, further applications of the procedure appear possible, although these are of a rather speculative nature at this time. The current mainstay of therapy-refractive hypertension is RSD, which is well supported by recent clinical data.

Calcium sparks in human ventricular cardiomyocytes from patients with terminal heart failure

Cardiomyocytes from terminally failing hearts display significant abnormalities in e-c-coupling, contractility and intracellular Ca(2+) handling. This study is the first to demonstrate the influence of end-stage heart failure on specific properties of Ca(2+) sparks in human ventricular cardiomyocytes. We investigated the frequency and characteristics of spontaneously arising Ca(2+) sparks in single isolated human myocytes from terminally failing (HF) and non-failing (NF) control myocardium by using the Ca(2+) indicator Fluo-3. The Ca(2+) sparks were recorded by line-scan images along the longitudinal axis of the myocytes at a frequency of 250Hz. After loading the sarcoplasmic reticulum (SR) with Ca(2+) by repetitive field stimulation (10 pulses at 1Hz) the frequency of the Ca(2+) sparks immediately after stimulation (t = 0s) was reduced significantly in HF compared to NF (4.15 +/- 0.42 for NF vs. 2.81 +/- 0.20 for HF sparks s(-1), P = 0.05). This difference was present constantly in line-scan recordings up to 15s duration (t = 15s: 2.75 +/- 0.65 for NF vs. 1.36 +/- 0.34 for HF sparks s(-1), P = 0.05). The relative amplitude (F/F(0)) of Ca(2+) sparks was also significantly lower in HF cardiomyocytes (1.33 +/- 0.015 NF vs. 1.19 +/- 0.003 HF, t = 0s) and during subsequent recordings of 15s. Significant differences between HF and NF were also present in calculations of specific spark properties. The time to peak was estimated at 25.75 +/-0.88ms in HF and 18.68 +/- 0.45ms in NF cardiomyocytes (P = 0.05). Half-time of decay was 66.48 +/- 1.89ms (HF) vs. 44.15 +/- 1.65ms (NF, P < 0.05), and the full width at half-maximum (FWHM) was 3.99 +/- 0.06 microm (HF) vs. 3.5 +/- 0.07 microm (NF, P < 0.05). These data support the hypothesis that even in the absence of cardiac disease, Ca(2+) sparks from human cardiomyocytes differ from previous results of animal studies with respect to the time-to-peak, half-time of decay and FWHM. The role of elevated external Ca(2+) in HF was studied by recording Ca(2+) sparks in HF cardiomyocytes with 10mmol external Ca(2+) concentration. Under these conditions, the average spark amplitude was increased from 1.19 +/- 0.003 (F/F(0), 2mmol Ca(2+)) to 1.26 +/- 0.01 (F/F(0), 10mmol Ca(2+)). We conclude that human heart failure causes distinct changes in Ca(2+) spark frequency and characteristics comparable to results established in animal models of heart failure. A reduced Ca(2+) load of the SR alone is unlikely to account for the observed differences between HF and NF and additional alterations in intracellular Ca(2+) release mechanisms must be postulated.

Identification of the cardiac ryanodine receptor channel in membrane blebs of sarcoplasmic reticulum

Blebs of the sarcoplasmic reticulum (SR) membrane of heart muscle cells were generated after saponin perforation of the plasma membrane followed by complete hypercontraction of the cell. Although characteristic proteins of the plasma membrane, namely the beta1-adrenoreceptor and Galphai, were stained by monoclonal antibodies in the hypercontracted cells, these proteins could not be detected in the adjacent blebs. Monoclonal antibodies to the cardiac ryanodine receptor (RyR2), calsequestrin and SERCA2 bound at different amounts to surface components of the blebs and to components of the hypercontracted cells. From the immunofluorescence signals we conclude that the blebs are mainly constituted of corbular and junctional SR membrane, and only to a lesser extent of network SR membrane. Deconvolution microscopy revealed that the membrane location of RyR2, calsequestrin and SERCA2 in the bleb is comparable to native SR membrane. At the bleb membrane giga-ohm seals could be obtained and patches could be excised in a way that single-channel currents could be measured, although these are not completely identified.

Characteristics of calcium sparks in cardiomyocytes derived from embryonic stem cells

In embryonic stem (ES) cell-derived cardiomyocytes, spontaneous Ca(2+) sparks representing Ca(2+) release through ryanodine receptor (RyR) channels were characterized and correlated to the expression of RyRs as well as the Ca(2+) load of the sarcoplasmic reticulum (SR). In very early developmental stage (VEDS) cardiac precursor cells, global intracellular Ca(2+) concentration ([Ca(2+)](i)) fluctuations occurred, whereas Ca(2+) sparks and contractions were absent. In early developmental stages (EDS), contractions as well as Ca(2+) sparks were obvious. During the further differentiation to late developmental stage (LDS) cardiomyocytes, a marked increase in the frequency of global [Ca(2+)](i) transients, the amplitude and the frequency of Ca(2+) sparks, as well as the expression of RyRs and the volume of RyR-positive SR, was observed. Furthermore, the caffeine-releasable SR Ca(2+) load was elevated in LDS compared with EDS cardiomyocytes. A high-Ca(2+) solution raised spark frequency as well as amplitude in EDS cardiomyocytes to the levels of LDS cardiomyocytes. The characteristics of Ca(2+) sparks occurring in cardiomyocytes differentiated from ES cells may be governed by the Ca(2+) load of the SR and/or the density of RyRs.

The ultrarapid and the transient outward K(+) current in human atrial fibrillation. Their possible role in postoperative atrial fibrillation

Atrial fibrillation (AF) causes distinct changes in atrial conduction, characterized as electrical remodeling. Experimental data on the possible significance of alterations of specific K(+)outward currents in this process are still limited in human AF. The ultra-rapid delayed rectifier current (I(Kur)) has not been studied in AF with respect to its sensitivity to 4-Aminopyridine (4-AP). To clarify the role of (1) the 4-AP sensitive I(Kur)current, compared to recordings without using 4-AP (I(Kur*)), and (2) the transient outward current (I(to)) in changes of atrial repolarization associated with AF, whole cell voltage-clamp recordings were obtained from atrial myocytes of patients undergoing elective cardiac surgery, with and without a history of atrial fibrillation (AF/non-AF). Further, a possible relation between experimental data and postoperative AF was studied. In AF patients, I(Kur*)was reduced by 40% [5.00+/-0.32 pA/pF (non-AF) and 2.91+/-0. 45 pA/pF (AF) at +50 mV, P<0.0001, n=22/11], I(Kur)by 55% [3.81+/-0. 30 pA/pF (non-AF) and 1.71+/-0.20 pA/pF (AF) at +50 mV, P<0.0001, n=22/11]. The mean amplitude of I(Kur)was significantly smaller than I(Kur*). Consistently, I(to)was reduced by 44% [11.57+/-0.77 pA/pF (non-AF) and 6.51+/-1.31 pA/pF (AF), P<0.01, n=25/11]. In 48% of non-AF patients, postoperative AF was detected. The corresponding voltage-clamp recordings showed a trend to reduced I(Kur*)and I(Kur)currents, although it did not reach statistical significance. The consistent reduction of all three K(+)currents investigated due to the presence of AF indicates an important association of abnormalities in cellular repolarization with the onset and the self-sustaining nature of human AF.

In vitro activity of various anthelmintic compounds against Haemonchus contortus larvae

Twenty-five known anthelmintic compounds were evaluated in vitro against the highly motile exsheathed non-feeding third-stage of Haemonchus contortus larvae. Activity was based on lack of motility or death of larvae after 24 h of chemical exposure. Six compounds (avermectins, closantel, levamisole, morantel, phenylhydrazone and ticarbodine) were active at a concentration of 100 micrograms cm-3 or less. The most active compounds were avermectins and levamisole. When higher in vitro concentrations were used, ten compounds (bephenium, coumaphos, dichlorovos, disophenol, hygromycin b, methyridine, parbendazole, phenothiazine, pyrantel and thiabendazole) exhibited activity. Nine compounds were found to be inactive; among these were the new benzimidazoles, i.e., albendazole, fenbendazole, mebendazole and oxibendazole. Because of the inactivity of the new benzimidazoles, this in vitro system is unsuitable as a routine screening tool. Also, the system appears to favor drugs that act quickly through percuticular entry. In an initial group of 5280 untested compounds, 254 (4.8%) exhibited in vitro activity at 100 micrograms cm-3 against the non-feeding larvae stage. The exogenous and in vitro cultivation techniques required for collecting, cleaning and exsheathing the larvae are described.