Current pressure on the UK imaging workforce deters imaging research in the NHS and requires urgent attention.

Medical imaging is a multidisciplinary specialty, combining clinical expertise from medical physics, radiography, and radiology, and plays a key role in patient care. Research is vital to ensure the care delivered to patients is evidence-based, and is a core component of clinical governance; however, there are pressures on the imaging workforce, which are significantly impeding imaging research. This commentary presents a research gap analysis pertaining to the multidisciplinary imaging workforce on behalf of the National Institute for Health Research (NIHR) Imaging Workforce Group. Data were summarised from membership surveys of the Royal College of Radiologists, Society and College of Radiographers, and Institute of Physics and Engineering in Medicine; national reports; and feedback from NIHR Clinical Research Network Imaging Champions meeting in 2020/2021. Common barriers to delivering research were found across the multidisciplinary workforce. The key issues were lack of staff, lack of time, and lack of funding to backfill clinical services. Given the ongoing workforce shortages and increasing clinical demands on radiologists, diagnostic radiographers, and medical physicists, these issues must be tackled with a high priority to ensure the future of clinical research within the NHS.

Simple dispersion estimate for single-section quantum-dash and quantum-dot mode-locked laser diodes.

The optical outputs of single-section quantum-dash and quantum-dot mode-locked lasers (MLLs) are well known to exhibit strong group velocity dispersion. Based on careful measurements of the spectral phase of the pulses from these MLLs, we confirm that the difference in group delay between the modes at either end of the MLL spectrum equals the cavity round-trip time. This observation allows us to deduce an empirical formula relating the accumulated dispersion of the output pulse to the spectral extent and free-spectral range of the MLL. We find excellent agreement with previously reported dispersion measurements of both quantum-dash and quantum-dot MLLs over a wide range of operating conditions.

Flexible terabit/s Nyquist-WDM super-channels using a gain-switched comb source.

Terabit/s super-channels are likely to become the standard for next-generation optical networks and optical interconnects. A particularly promising approach exploits optical frequency combs for super-channel generation. We show that injection locking of a gain-switched laser diode can be used to generate frequency combs that are particularly well suited for terabit/s super-channel transmission. This approach stands out due to its extraordinary stability and flexibility in tuning both center wavelength and line spacing. We perform a series of transmission experiments using different comb line spacings and modulation formats. Using 9 comb lines and 16QAM signaling, an aggregate line rate (net data rate) of 1.296 Tbit/s (1.109 Tbit/s) is achieved for transmission over 150 km of standard single mode fiber (SSMF) using a spectral bandwidth of 166.5 GHz, which corresponds to a (net) spectral efficiency of 7.8 bit/s/Hz (6.7 bit/s/Hz). The line rate (net data rate) can be boosted to 2.112 Tbit/s (1.867 Tbit/s) for transmission over 300 km of SSMF by using a bandwidth of 300 GHz and QPSK modulation on the weaker carriers. For the reported net data rates and spectral efficiencies, we assume a variable overhead of either 7% or 20% for forward- error correction depending on the individual sub-channel quality after fiber transmission.

Choice of biodiversity index drives optimal fire management decisions.

Preservation of biodiversity is a central goal of conservation management, yet the conditions that promote persistence may differ for the species in the community. For systems subject to stochastic disturbances such as fire, understanding which management practices promote persistence for all species in a community is complex. Before deciding on the best course of action, an objective must be specified. Yet an overarching goal of species persistence can be specified into a measureable objective many different ways. We investigated four alternative management objectives for maximizing species persistence that use common biodiversity indices: (1) attaining the minimally acceptable mix of successional vegetation states to support species' relative abundances, (2) maximizing the arithmetic mean abundance of species, (3) maximizing the geometric mean abundance of species, and (4) minimizing the average extinction risk of species. We used stochastic dynamic programming to model successional changes in vegetation in the presence of both planned and unplanned fires, and utilize an extensive data set on the occurrence of birds, reptiles, and small mammals in different successional states in semiarid Australia. We investigated the influence the choice of objective function and taxonomic focus has on the optimal fire management recommendations. We also evaluated a recent hazard reduction policy to annually burn a fixed amount of the landscape and compare results to the optimal solution. The optimal management strategy to maximize species persistence over a 100-year period is predominantly to minimize wildfires. This is because the majority of species are more likely to occur in intermediate, and late successional vegetation. However the optimal solution showed sensitivity to the objective and the species included in the analysis. These results highlight the need for careful consideration when specifying an objective to represent overarching conservation goals. Using the extinction risk objective, we show that a policy to annually burn 5% of the landscape could increase the average probability of extinction for the modelled species by 7% over the next 100 years compared to the optimal management scenario.

Smoky homes: gender, socioeconomic and housing disparities in second hand tobacco smoke (SHS) exposure in a large population-based Australian cohort.

OBJECTIVE: Although research suggests that socioeconomic status (SES) will be related to housing type with regard to second-hand smoke (SHS) exposure, there has been no comprehensive examination of these relationships. This study aimed to explore associations between SHS exposure a) at home and b) at other places, and a number of SES, housing, and health factors. METHOD: Data were drawn from the 45 and Up Study, a large cohort study with 266,848 adults in New South Wales, Australia, of which 160,824 participants aged 45-65years were included in this study. Associations between socio-demographic characteristics, smoking status, housing-type, SES, and exposure to SHS were explored initially using Chi-square tests. Ordinal logistic models were created with increasing exposure to SHS at home and at other places. RESULTS: When measuring SHS exposure at home, being female (odds ratio (OR)=1.2, 95% confidence interval (CI)=1.2, 1.3); being of lower age (45-49years vs 60-64years, OR=1.4, 95%CI=1.3, 1.5), being a current smoker of over 20 cigarettes per day (vs never smoked, OR=10.2, 95%CI=9.4,11); living in other types of dwelling compared to living at home (OR=1.3, 95%CI=1.1, 1.4), living with a partner (vs being single OR=2.3, 95%CI=2.1, 2.5), and low SES measures were associated with increased exposure. Increasing SHS exposure at other places was also related to low SES measures, however unlike SHS exposure at home, SHS exposure at other places was associated with being male (OR=1.5, 95%CI=1.5, 1.6); and greater paid hours of work (OR=1.3, 95%CI=1.2, 1.3). CONCLUSION: Improved monitoring of SHS exposure in high risk environments is required. Tailoring SHS messages to environments may also be required, for example to women living in units, apartments and mobile homes and males in lower income workplaces.

Measuring the correlation of two optical frequencies using four-wave mixing.

We use the physics of four-wave mixing to study the decorrelation of two optical frequencies as they propagate through different fiber delays. The phase noise relationship between the four-wave mixing components is used to quantify and measure the correlation between the two optical frequencies using the correlation coefficient. We show the difference in the evolution of decorrelation between frequency-dependent and frequency-independent components of phase noise.

AI implementation in the UK landscape: Knowledge of AI governance, perceived challenges and opportunities, and ways forward for radiographers.

INTRODUCTION: Despite the rapid increase of AI-enabled applications deployed in clinical practice, many challenges exist around AI implementation, including the clarity of governance frameworks, usability of validation of AI models, and customisation of training for radiographers. This study aimed to explore the perceptions of diagnostic and therapeutic radiographers, with existing theoretical and/or practical knowledge of AI, on issues of relevance to the field, such as AI implementation, including knowledge of AI governance and procurement, perceptions about enablers and challenges and future priorities for AI adoption. METHODS: An online survey was designed and distributed to UK-based qualified radiographers who work in medical imaging and/or radiotherapy and have some previous theoretical and/or practical knowledge of working with AI. Participants were recruited through the researchers' professional networks on social media with support from the AI advisory group of the Society and College of Radiographers. Survey questions related to AI training/education, knowledge of AI governance frameworks, data privacy procedures, AI implementation considerations, and priorities for AI adoption. Descriptive statistics were employed to analyse the data, and chi-square tests were used to explore significant relationships between variables. RESULTS: In total, 88 valid responses were received. Most radiographers (56.6 %) had not received any AI-related training. Also, although approximately 63 % of them used an evaluation framework to assess AI models' performance before implementation, many (36.9 %) were still unsure about suitable evaluation methods. Radiographers requested clearer guidance on AI governance, ample time to implement AI in their practice safely, adequate funding, effective leadership, and targeted support from AI champions. AI training, robust governance frameworks, and patient and public involvement were seen as priorities for the successful implementation of AI by radiographers. CONCLUSION: AI implementation is progressing within radiography, but without customised training, clearer governance, key stakeholder engagement and suitable new roles created, it will be hard to harness its benefits and minimise related risks. IMPLICATIONS FOR PRACTICE: The results of this study highlight some of the priorities and challenges for radiographers in relation to AI adoption, namely the need for developing robust AI governance frameworks and providing optimal AI training.

Dual correlated pumping scheme for phase noise preservation in all-optical wavelength conversion.

We study the effect of transfer of phase noise in different four wave mixing schemes using a coherent phase noise measurement technique. The nature of phase noise transfer from the pump to the generated wavelengths is shown to be independent of the type of phase noise (1 / f or white noise frequency components). We then propose a novel scheme using dual correlated pumps to prevent the increase in phase noise in the conjugate wavelengths. The proposed scheme is experimentally verified by the all-optical wavelength conversion of a DQPSK signal at 10.7 GBaud.

Screening, brief intervention, and referral to treatment (SBIRT) for cannabis: A scoping review.

INTRODUCTION: Screening, brief intervention, and referral to treatment (SBIRT) has been used to change substance use behavior. Despite cannabis being the most prevalent federally illicit substance, we have limited understanding of use of SBIRT for managing cannabis use. This review aimed to summarize the literature on SBIRT for cannabis use across age groups and contexts over the last two decades. METHODS: This scoping review followed the a priori guide outlined by the PRISMA (Preferred Reporting Items for Scoping Reviews and Meta-Analyses) statement. We gathered articles from PsycINFO, PubMed, Sage Journals Online, ScienceDirect, and SpringerLink. RESULTS: The final analysis includes forty-four articles. Results indicate inconsistent implementation of universal screens and suggest screens assessing cannabis-specific consequences and utilizing normative data may increase patient engagement. Broadly, SBIRT for cannabis demonstrates high acceptability. However, the impact of SBIRT on behavior change across various modifications to intervention content and modality has been inconsistent. In adults, patients with primary cannabis use are not engaging in recommended treatment at similar rates to other substances. Results also suggest a lack of research addressing referral to treatment in adolescents and emerging adults. DISCUSSION: Based on this review, we offer several to improve each component of SBRIT that may increase implementation of screens, effectiveness of brief interventions, and engagement in follow-up treatment.

UK reporting radiographers' perceptions of AI in radiographic image interpretation - Current perspectives and future developments.

INTRODUCTION: Radiographer reporting is accepted practice in the UK. With a national shortage of radiographers and radiologists, artificial intelligence (AI) support in reporting may help minimise the backlog of unreported images. Modern AI is not well understood by human end-users. This may have ethical implications and impact human trust in these systems, due to over- and under-reliance. This study investigates the perceptions of reporting radiographers about AI, gathers information to explain how they may interact with AI in future and identifies features perceived as necessary for appropriate trust in these systems. METHODS: A Qualtrics® survey was designed and piloted by a team of UK AI expert radiographers. This paper reports the third part of the survey, open to reporting radiographers only. RESULTS: 86 responses were received. Respondents were confident in how an AI reached its decision (n = 53, 62%). Less than a third of respondents would be confident communicating the AI decision to stakeholders. Affirmation from AI would improve confidence (n = 49, 57%) and disagreement would make respondents seek a second opinion (n = 60, 70%). There is a moderate trust level in AI for image interpretation. System performance data and AI visual explanations would increase trust. CONCLUSIONS: Responses indicate that AI will have a strong impact on reporting radiographers' decision making in the future. Respondents are confident in how an AI makes decisions but less confident explaining this to others. Trust levels could be improved with explainable AI solutions. IMPLICATIONS FOR PRACTICE: This survey clarifies UK reporting radiographers' perceptions of AI, used for image interpretation, highlighting key issues with AI integration.

Research ethics systems, processes, and awareness across Europe: Radiography research ethics standards for Europe (RRESFE).

INTRODUCTION: The Radiography Research Ethics Standards for Europe (RRESFE) project aims to provide a cross-sectional snapshot of current research ethics systems, processes, and awareness of such, across Europe together with identifying the associated challenges, education, and training needs. METHODS: A cross-sectional online survey targeting radiography researchers in Europe was conducted. Data collection took place between April 26 and July 12, 2021, using a snowball sampling approach. Descriptive and analytical statistics were used to identify trends in research ethics frameworks across Europe. RESULTS: 285 responses were received across 33 European and 23 non-European countries. Most (n = 221; 95%) European respondents stated ethics approval is required before commencing research in their country. Requirements around research ethics approval and awareness of such requirements varied by European region (X2 (2, n = 129) = 7.234, p = 0.013) and were found to differ depending on the type of research participant and study design. Additionally, European respondents reported ethics approval is a national requirement more often than their non-European counterparts (X2 (1, n = 282) = 4.316, p = 0.049). Requirements for ethics approval were also associated with the undergraduate programme duration (2-year vs. 3-year vs. 3.5 year vs. 4-year vs. multiple programme durations; X2 (4, n = 231) = 10.075, p = 0.016) and availability of postgraduate training (postgraduate training available vs. postgraduate training not available; X2 (1, n = 231) = 15.448, p = <0.001) within respondents' country. CONCLUSION: Respondents from countries with longer programme durations/availability of multiple programme lengths, availability of postgraduate training, and establishment of European Qualifications Framework Level 6 were generally associated with less uncertainty and more comprehensive research ethics requirements. IMPLICATIONS FOR PRACTICE: Results are informative of the current status of research ethics within evidence-based radiography.

Research ethics training, challenges, and suggested improvements across Europe: Radiography research ethics standards for Europe (RRESFE).

INTRODUCTION: The Radiography Research Ethics Standards for Europe (RRESFE) project aimed to provide a cross-sectional view of the current state of radiography research ethics across Europe. This included investigating education and training in research ethics, and identifying the key challenges and potential improvements associated with using existing research ethics frameworks. METHODS: This cross-sectional online survey targeting radiography researchers in Europe was conducted between April 26 and July 12, 2021. Descriptive and analytical statistics were used to identify research ethics education and training trends. Content analysis of qualitative responses was employed to identify significant challenges and proposed improvements in research ethics frameworks of practice. RESULTS: There were 232 responses received across 33 European countries. Most (n = 132; 57%) respondents had received some research ethics training; however, fewer participants had received training on safeguarding vulnerable patients (n = 72; 38%), diversity and inclusivity (n = 62; 33%), or research with healthy volunteers (n = 60; 32%). Training was associated with a greater perceived importance of the need for research ethics review (p = 0.031) and with the establishment of EQF Level 6 training (p = 0.038). The proportion of formally trained researchers also varied by region (p = <0.001). Time-to-ethics-approval was noted as the biggest challenge for professionals making research ethics applications. CONCLUSION: Early and universal integration of research-oriented teaching within the radiography education framework which emphasises research ethics is recommended. Additionally, study findings suggest research ethics committee application and approval processes could be further simplified and streamlined. IMPLICATIONS FOR PRACTICE: The survey contributes to a growing body of knowledge surrounding the importance of education and training in research ethics for assuring a high standard of research outputs in Radiography and has identified hurdles to obtaining research ethics approval for further investigation and address.

The College of Radiographers Research Strategy for the next five years.

This article outlines the updated College of Radiographers (CoR) Research Strategy. This new research strategy will shape the approach to research from the radiography profession over the next five years. This will apply to all the profession and is aspirational and future thinking. The updated research strategy is the fifth research strategy presented by the CoR. Over the last five years, there have been considerable developments within healthcare and healthcare research. As this article is being written we are still in the middle of a global pandemic (Covid-19) which has influenced all our lives. However, despite the challenges of the last year, we are in a stronger position as a profession with more radiographers working towards and gaining masters and doctoral level qualifications. There are more radiographers working in clinical academic roles and there has been further development of radiographers coordinating and delivering research as well as becoming research leaders. This updated research strategy supports the radiography profession in delivering research-based practice over the next five years offering a framework within which radiographers can develop.

Artificial Intelligence: Guidance for clinical imaging and therapeutic radiography professionals, a summary by the Society of Radiographers AI working group.

INTRODUCTION: Artificial intelligence (AI) has started to be increasingly adopted in medical imaging and radiotherapy clinical practice, however research, education and partnerships have not really caught up yet to facilitate a safe and effective transition. The aim of the document is to provide baseline guidance for radiographers working in the field of AI in education, research, clinical practice and stakeholder partnerships. The guideline is intended for use by the multi-professional clinical imaging and radiotherapy teams, including all staff, volunteers, students and learners. METHODS: The format mirrored similar publications from other SCoR working groups in the past. The recommendations have been subject to a rapid period of peer, professional and patient assessment and review. Feedback was sought from a range of SoR members and advisory groups, as well as from the SoR director of professional policy, as well as from external experts. Amendments were then made in line with feedback received and a final consensus was reached. RESULTS: AI is an innovative tool radiographers will need to engage with to ensure a safe and efficient clinical service in imaging and radiotherapy. Educational provisions will need to be proportionately adjusted by Higher Education Institutions (HEIs) to offer the necessary knowledge, skills and competences for diagnostic and therapeutic radiographers, to enable them to navigate a future where AI will be central to patient diagnosis and treatment pathways. Radiography-led research in AI should address key clinical challenges and enable radiographers co-design, implement and validate AI solutions. Partnerships are key in ensuring the contribution of radiographers is integrated into healthcare AI ecosystems for the benefit of the patients and service users. CONCLUSION: Radiography is starting to work towards a future with AI-enabled healthcare. This guidance offers some recommendations for different areas of radiography practice. There is a need to update our educational curricula, rethink our research priorities, forge new strong clinical-academic-industry partnerships to optimise clinical practice. Specific recommendations in relation to clinical practice, education, research and the forging of partnerships with key stakeholders are discussed, with potential impact on policy and practice in all these domains. These recommendations aim to serve as baseline guidance for UK radiographers. IMPLICATIONS FOR PRACTICE: This review offers the most up-to-date recommendations for clinical practitioners, researchers, academics and service users of clinical imaging and therapeutic radiography services. Radiography practice, education and research must gradually adjust to AI-enabled healthcare systems to ensure gains of AI technologies are maximised and challenges and risks are minimised. This guidance will need to be updated regularly given the fast-changing pace of AI development and innovation.

Ventricular arrhythmias related to antibiotic usage in dogs.

In dogs, pretreatment with the macrolide antibiotic tylosin (5 milligrams per day per kilogram of body weight) increased the incidence of ventricular tachycardia and fibrillation during acute myocardial ischemia. Another group received a dose of acetyl strophanthidin which was nontoxic in controls, but which resulted in a ventricular arrhythmia in six of seven animals on antibiotic treatment. Enhancement of loss of potassium ion from the myocardium by the antibiotic was presumed to be related to the altered cardiac rhythm.

A review of visual ethnography: Radiography viewed through a different lens.

INTRODUCTION: The objective of this article is to provide a short review of the research methodology 'visual ethnography'. METHOD: The review article will provide a summary of the foundations of visual ethnography, outline the key debates and refer to some of the main authors working in this field. RESULTS: Visual Ethnography is both a methodology and a method of research. It should be selected for research in radiography when research questions seek to focus upon aspects or elements of a culture. A research plan that is designed using a visual ethnographic approach should be flexible and take into account the requirements of the researcher and research participants. Visual methods of research include the use of various images, for example, photographs, collage, film or drawings. Visual methods are commonly employed together with interviews, conversations and observation. The approach enables researchers to generate new and unique insights into cultures. CONCLUSION: This review of visual ethnography provides background information that informs an introduction to the methodology. It demonstrates a methodology with the potential to explore culture and expand knowledge of radiography practice. IMPLICATIONS FOR PRACTICE: The authors suggest that for future studies visual ethnography is a methodology that can expand the paradigm of radiography research.

Case reports: lisinopril-induced erythroderma in an 85-year-old male.

An 85-year-old male presented with a case of erythroderma secondary to lisinopril ingestion without a previous history of skin disease. While ACE inhibitors have been shown to elicit psoriatic erythroderma in previous cases, to our knowledge this is the first case report of iatrogenic erythroderma secondary to lisinopril in a patient without dermatologic comorbidities.

Origin of acetyl strophanthidin-induced ventricular arrhythmias.

To examine the origin of digitalis-induced ventricular tachycardia (VT), acetyl strophanthidin (AS) (25 mug/min) was perfused into a limited zone of myocardium in intact anesthetized dogs through a catheter placed fluoroscopically in the left anterior descending artery without ischemia. A second catheter in the great cardiac vein sampled venous effluent from this region. His and left bundle branch depolarizations were recorded and bipolar intramural electrograms from endocardial and epicardial sites within the anterior descending region were obtained. No conduction alterations preceded arrhythmia. Cardiac venous K+ rose from 3.3 +/- to 4.4 +/- 0.2 meq/liter (P less than 0.001), indicating egress from the perfused zone. 10 animals (Group 1) were sacrificed 2 min after onset of VT while 11 (Group 2) continued until fibrillation (4-14 min). All showed normal (endocardial leads to epicardial) transmural depolarization during sinus rhythm, but 10/21 demonstrated reversal, usually late during VT, including 8/11 in Group 2. Epicardial activation preceded fascicular activation and QRS. Recordings from the border and circumflex regions in 10 additional dogs (Group 3) demonstrated activation reversal only in the border zone. Myocardial K+ was reduced (mean 63 +/- 1 mueq/g) and Na+ increased (mean 41 +/- 2 mueq/g) in the perfused zone (nonperfused circumflex area K+ 72 +/- 1, Na+ 33 +/- 1 mueq/g, P less than 0.001 for both); changes were similar in inner and outer ventricular wall. In related experiments, subepicardial injections of AS induced activation reversal within the immediate area, similar to recordings during coronary infusion. Reversed transmural activation with early epicardial depolarization suggest VT arises within myocardium; electrolyte gradients between adjacent regions may be causative.

Sustained effect of glucose-insulin-potassium on myocardial performance during regional ischemia. Role of free fatty acid and osmolality.

To evaluate the influence of glucose infusate administered with insulin and potassium on left ventricular function during 4 h of ischemia, as well as mechanism of action, four groups of intact anesthetized dogs were studied. Acute regional ischemia was induced with a balloon tip catheter in the left anterior descending artery and infusates were begun after 20 min of ischemia. A threefold increase of plasma glucose concentration was associated with improved left ventricular function during ischemia, compared to animals receiving isovolumic saline. There was a significant decline of left ventricular end-diastolic pressure associated with elevation of stroke volume and ejection fraction to control levels, as determined by indicator dilution. In a separate subgroup studied by cineangiography, shortening of the ischemic anterior wall, after an initial decline, was increased in response to glucose but there was no evidence of extension of injury. Ischemic tissue exhibited a smaller gain of water as well as Na+ per gram dry weight as compared to ischemic controls. On precordial electrocardiogram mapping there was a significant decrease in the sigmaST (sum of ST elevation) as well as NST (number of ST segment elevations), but the reduction of R wave amplitude was not different from controls. To further evaluate long-term effects, eight controls and six treated animals underwent myocardial ischemia and were sacrificed after 4 mo. Calculated area and weight of scar, as well as degree of wall thinning, were similar in both groups. The glucose-treated animals had a significant decrease of plasma FFA in contrast to controls which manifested a significant rise. To examine the postulate that the decrease in FFA was important to therapeutic action, a third group was infused with Intralipid (Cutter Laboratories, Inc., Berkeley, Calif.) and heparin, simultaneously with the glucose infusate, to effect an elevation of plasma FFA during ischemia. Changes in myocardial function and electrolyte composition, as well as precordial electrocardiogram mapping, were similar to that of animals receiving glucose alone. Because serum osmolality was increased approximately 40 mosmol during the glucose infusion, the potential role of hyperosmolality was assessed by infusion of 20% mannitol during acute ischemia in a fourth group. After a transient small increase, there was a moderate decline in function by 4 h, suggesting that the response to glucose is not dependent upon extracellular osmolality. Thus, it is concluded that during the initial hours after the onset of myocardial ischemia the glucose infusate improves ventricular performance without evidence of arrhythmia induction or intensification of ischemic injury. Evolution of irreversible necrosis appears to be delayed rather than prevented under the circumstances of this study.

Arrhythmia susceptibility and myocardial composition in diabetes. Influence of physical conditioning.

Abnormal myocardial composition in diabetes mellitus has been described, but the effects on ventricular vulnerability have not been defined. We have assessed the susceptibility to arrhythmias in a canine model after 1 yr of mild diabetes induced by alloxan. Since physical conditioning can affect metabolic abnormalities in diabetes, this intervention has also been evaluated. Group 1 served as controls and groups 3 and 4 were diabetic. Animals in the latter group as well as nondiabetic controls of group 2 were exercised on a treadmill for the last 8 mo of the experiment. After 1 yr, anesthesia was induced with chloralose for vulnerability studies. The ventricular fibrillation threshold of 24.4 +/- 1.9 mA in group 3 was significantly less than in normals (45.1 +/- 2.2). Spontaneous arrhythmias were also more prevalent in diabetics during acute ischemia (group 3-A). Increased ventricular vulnerability after epinephrine infusion was present in the sedentary diabetes despite normal ventricular function responsiveness. In a superfused preparation of myocardium, resting membrane potential and action potential amplitude were normal in diabetics, and beta-adrenergic stimulation shortened repolarization more than in controls. Myocardial collagen concentrations, which included an interfibrillar distribution on morphologic examination, were increased in group 3. In the trained diabetics of group 4 the basal vulnerability thresholds and responses to epinephrine were normal. While myocardial collagen levels were normal, cholesterol and triglyceride increments persisted. Thus, in mild experimental diabetes, enhanced susceptibility to arrhythmias exists; this susceptibility may be based on a combination of nonhomogenous collagen accumulation affecting local conduction and increased electrophysiologic sensitivity to catecholamines.