Impact of legislative reform on worker fatalities in New Zealand workplaces: a 30-year retrospective population-level analysis.

OBJECTIVES: To determine the impact of major legislative changes to New Zealand's Occupational Health and Safety (OHS) legislation with the adoption of the Robens model as a means to control occupational risks on the burden and risk of work-related fatal injury (WRFI). METHODS: Population-based comparison of WRFI to workers aged 15-84 years occurring during three periods: before (pre:1985-1992), after legislative reform (post-1:1993-2002) and after subsequent amendment (post-2:2003-2014). Annual age-industry standardised rates were calculated with 95% CI. Multivariable Poisson regression was used to estimate age-adjusted annual percentage changes (APC) for each period, overall and stratified by high-risk industry and occupational groups. RESULTS: Over the 30-year period, 2053 worker deaths met the eligibility criteria. Age-adjusted APC in rates of worker WRFI changed little between periods: pre (-2.8%, 95% CI 0.0% to -5.5%); post-1 (-2.9%, 95% CI -1.3% to -4.5%) and post-2 (-2.9%, 95% CI -1.3% to -4.4%). There was no evidence of differences in slope. Variable trends in worker WRFI were observed for historically high-risk industry and occupational groups. CONCLUSIONS: The rate of worker WRFI decreased steadily over the 30-year period under examination and there was no evidence that this pattern of declining WRFI was substantially altered with the introduction of Robens-styled OHS legislative reforms. Beyond headline figures, historically high-risk groups had highly variable progress in reducing worker WRFI following legislative reform. This study demonstrates the value in including prereform data and high-risk subgroup analysis when assessing the performance of OHS legislative reforms to control occupational risks.

Missing cases of injury death: use of quantitative methods and case reviews to inform future improvements in case definition.

BACKGROUND: Knowledge of fatal injuries is required to inform prevention activities. Where hospital patients with an injury principal diagnosis (PDx) died and were certified to a medical underlying cause of death (UCoD), there is the potential to underestimate injury mortality. We sought to characterise injury/non-injury (NI) mismatches between PDx and UCoD by identifying which subgroups had small/large mismatches, and to understand why mismatches had occurred using informative examples. METHOD: Hospital records (n=10 234) with a PDx of injury were linked to the mortality collection using a unique personal identifier. Percentages UCoD coded to a NI were tabulated, for three follow-up periods and by selected variables. Additionally, we reviewed a sample of 70 records for which there was a mismatch. RESULTS: %NIs were 39%, 66% and 77% for time from injury to death of <1 week, <90 days and <1 year, respectively. Variations in %NI were found for all variables. Illustrative examples of 70 medical UCoD deaths showed that for 12 cases the injury event was unequivocally judged to have resulted in premature death. A further 16 were judged as injury deaths using balance of probability arguments. CONCLUSION: There is variation in rates of mismatch between PDx of injury and UCoD of NI. While legitimate reasons exist for mismatches in certain groups, a material number of injury deaths are not captured using UCoD alone; a new operational definition of injury death is needed. Early solutions are proposed. Further work is needed to investigate operational definitions with acceptable false positive and negative detection rates.

Use of mixed methods to investigate case definitions to improve the identification of serious injury cases from hospital episode data.

INTRODUCTION: It has been commonplace internationally, when using hospital data, to use the principal diagnosis to identify injury cases and the first external cause of injury code (E-code) to identify the main cause. Our purpose was to investigate alternative operational definitions of serious non-fatal injury to identify cases of interest for injury surveillance, both overall and for four common causes of injury. METHODS: Serious non-fatal injury cases were identified from New Zealand (NZ) hospital discharge data using an alternative definition: that is, case selection using principal and additional diagnoses. Separately, identification of cause used all E-codes on the discharge record. Numbers of cases identified were contrasted with those captured using the usual definition. Views of NZ government stakeholders were sought regarding the acceptability of the additional cases found using these alternative definitions. Views of international experts were also canvassed. RESULTS: When using all diagnoses there was a 7% increase in 'all injury' cases identified, a 17% increase in self-harm cases and 8% increase in falls cases. Use of all E-codes resulted in a 4% increase in self-harm cases, 2% increase in assault cases and 1% increase in both falls and motor vehicle traffic crash cases. DISCUSSION: A case definition based solely on principal diagnosis fails to count a material number of serious non-fatal injury cases that are of interest to the injury prevention community. There is a need, therefore, to use an alternative case definition that includes additional diagnoses. Use of multiple E-codes to classify cause of injury should be considered.

Using hospital discharge data for injury research or surveillance? An observational study illustrating the impact of administrative change.

INTRODUCTION: Hospital discharge data provide an important basis for determining priorities for injury prevention and monitoring trends in incidence. This study aims to illustrate the impact of a recent change in administrative practice on estimates of hospitalised injury incidence and to investigate the extent to which different case selection affects trends in injury incidence rates. METHODS: New Zealand (NZ) hospital discharges (2000-2014) with a primary diagnosis of injury were identified. Additional case selection criteria included first admissions only, and for serious injury, a high threat-to-life estimate. Comparisons were made, over time and by District Health Board, between hospitalised injury incidence estimates that included, or not, short-stay emergency department (SSED) discharges. RESULTS: Of the 1 229 772 injury hospital discharges, 365 114 were SSED; 16% of the annual total in 2000, 38% in 2014. Identification of readmissions prior to the exclusion of SSED discharges resulted in 30 724 cases being erroneously removed. Age-standardised rates of hospitalised injury over the 15-year period increased by, on average, 2.7% per year when SSED discharges were included; there was minimal secular change (-0.2%) when SSEDs were excluded. For serious hospitalised injury, the annual increase was 2.3% when SSED was included compared with 1.1% when SSEDs were excluded. CONCLUSION: Spurious trends in hospitalised injury incidence can result when administrative practices are not appropriately accounted for. Exclusion of SSED discharges before the identification of readmissions and the use of a severity threshold are recommended to minimise the reporting bias in NZ hospitalised injury incidence estimates.

Empirical validation of the New Zealand serious non-fatal injury outcome indicator for 'all injury'.

Our purpose was to empirically validate the official New Zealand (NZ) serious non-fatal 'all injury' indicator. To that end, we aimed to investigate the assumption that cases selected by the indicator have a high probability of admission. Using NZ hospital in-patient records, we identified serious injury diagnoses, captured by the indicator, if their diagnosis-specific survival probability was ≤0.941 based on at least 100 admissions. Corresponding diagnosis-specific admission probabilities from regions in Canada, Denmark and Greece were estimated. Aggregate admission probabilities across those injury diagnoses were calculated and inference made to New Zealand. The admission probabilities were 0.82, 0.89 and 0.90 for the regions of Canada, Denmark and Greece, respectively. This work provides evidence that the threshold set for the official New Zealand serious non-fatal injury indicator for 'all injury' captures injuries with high aggregate admission probability. If so, it is valid for monitoring the incidence of serious injuries.

Towards valid 'serious non-fatal injury' indicators for international comparisons based on probability of admission estimates.

BACKGROUND: Governments wish to compare their performance in preventing serious injury. International comparisons based on hospital inpatient records are typically contaminated by variations in health services utilisation. To reduce these effects, a serious injury case definition has been proposed based on diagnoses with a high probability of inpatient admission (PrA). The aim of this paper was to identify diagnoses with estimated high PrA for selected developed countries. METHODS: The study population was injured persons of all ages who attended emergency department (ED) for their injury in regions of Canada, Denmark, Greece, Spain and the USA. International Classification of Diseases (ICD)-9 or ICD-10 4-digit/character injury diagnosis-specific ED attendance and inpatient admission counts were provided, based on a common protocol. Diagnosis-specific and region-specific PrAs with 95% CIs were calculated. RESULTS: The results confirmed that femoral fractures have high PrA across all countries studied. Strong evidence for high PrA also exists for fracture of base of skull with cerebral laceration and contusion; intracranial haemorrhage; open fracture of radius, ulna, tibia and fibula; pneumohaemothorax and injury to the liver and spleen. Slightly weaker evidence exists for cerebellar or brain stem laceration; closed fracture of the tibia and fibula; open and closed fracture of the ankle; haemothorax and injury to the heart and lung. CONCLUSIONS: Using a large study size, we identified injury diagnoses with high estimated PrAs. These diagnoses can be used as the basis for more valid international comparisons of life-threatening injury, based on hospital discharge data, for countries with well-developed healthcare and data collection systems.

The epidemiology of life-threatening work-related injury--a demonstration paper.

BACKGROUND: Workers' compensation (WC) data traditionally provides information to stakeholders on work-related disabling injuries. It is important to complement this with information on serious threat to life (TTL) injury, which is the focus of this paper. METHODS: In this cross-sectional descriptive epidemiological study, based on New Zealand's WC data linked to hospital discharge data, TTL was measured using the ICD10-based Injury Severity Score (ICISS); ICISS ≤ 0.941 was used to define serious TTL injury. RESULTS: During 2002-2004, there was an average of 368 serious TTL work-related injury cases annually. The distribution of these injuries was very different from those traditionally found using WC data to describe disabling injury. For example, for serious TTL injury the main injury types included traumatic brain injury, whereas for disabling injury it was sprains and dislocations. CONCLUSIONS: The method presented provides the opportunity for government agencies to produce a national description of the epidemiology of serious TTL work-related injuries.

An outcome evaluation of a New Zealand farm safety intervention: a historical cohort study.

BACKGROUND: There is limited evidence that farm safety-related interventions based solely on an educational element have an effect on injury rates. Our aim was to evaluate a New Zealand national educational program, FarmSafe™ Awareness, for its effect on injury rates. METHODS: We used a before-after design followed by a historical cohort study of sheep, beef, and dairy farmers/workers. The outcomes were work-related injuries, identified from workers compensation data. Cox regressions were used to compare intervention with matched control group rates. RESULTS: FarmSafe™ Awareness was associated with significantly higher rates of work-related injury, than matched controls. CONCLUSIONS: It is difficult to see how FarmSafe™ Awareness could be causing an increased rate of work-related injury. We detected no reporting bias, and selection bias is likely to act in the opposite direction to the observed results. We conclude that there is no evidence that FarmSafe™ Awareness prevents farm injury.

Measuring the population burden of fatal and nonfatal injury.

The value of measuring the population burden of fatal and nonfatal injury is well established. Population health metrics are important for assessing health status and health-related quality of life after injury and for integrating mortality, disability, and quality-of-life consequences. A frequently used population health metric is the disability-adjusted life-year. This metric was launched in 1996 in the original Global Burden of Disease and Injury study and has been widely adopted by countries and health development agencies alike to identify the relative magnitude of different health problems. Apart from its obvious advantages and wide adherence, a number of challenges are encountered when the disability-adjusted life-year is applied to injuries. Validation of disability-adjusted life-year estimates for injury has been largely absent. This paper provides an overview of methods and existing knowledge regarding the population burden of injury measurement. The review of studies that measured burden of injury shows that estimates of the population burden remain uncertain because of a weak epidemiologic foundation; limited information on incidence, outcomes, and duration of disability; and a range of methodological problems, including definition and selection of incident and fatal cases, choices in selection of assessment instruments and timings of use for nonfatal injury outcomes, and the underlying concepts of valuation of disability. Recommendations are given for methodological refinements to improve the validity and comparability of future burden of injury studies.

The New Zealand serious non-fatal self-harm indicators: how valid are they for monitoring trends?

BACKGROUND: To monitor accurately injury incidence trends, indicators should measure incidence independently of extraneous factors. Frequencies and rates of New Zealand's serious non-fatal self-harm indicators may be prone to fluctuations in reporting owing, for example, to changing social norms. Hence, they have been considered provisional. AIM: To validate empirically the serious non-fatal self-harm indicators. Methods All serious non-fatal first admissions to hospital were identified and classified according to whether principal diagnosis (PDx) was injury or mental disorder, and conversely whether contributing diagnoses were mental disorder or injury. The proportion assigned self-harm external cause of injury code (E-code) was calculated for each year from 2001 to 2007. Subsequently, all cases with a self-harm E-code were identified, and the proportion with a PDx of injury and contributing diagnosis of mental disorder, or PDx of mental disorder and contributing diagnosis of injury over time, were determined. RESULTS: No linear changes over time were detected in the proportion of cases assigned an injury PDx, or the proportion assigned a mental disorder PDx, or the proportion with a self-harm E-code. The estimated maximum observed increase in the frequency of serious non-fatal self-harm hospitalisation explained by changes in reporting was 19- 40%. CONCLUSION: Identification of serious non-fatal self-harm events using an operational definition of PDx of injury, a self-harm first listed E-code, and an appropriate severity cut-off point, is a valid method of monitoring incidence and rates in New Zealand.

Injury mortality indicators: recommendations from the International Collaborative Effort on Injury Statistics.

BACKGROUND: The International Collaborative Effort (ICE) on Injury Statistics called for an effort 'to reach consensus on what are the 10 most important indicators of injury incidence that offer the potential for international comparisons and for regional or global monitoring.' OBJECTIVES: To describe the process of developing the ICE indicators and to present the specifications of selected injury mortality indicators, along with comparisons between selected countries for those specified indicators. METHODS: Participants on the ICE list had been asked to send to one of the authors what they considered the most important five indicators of injury incidence. These were synthesised and presented under six themes: mortality indicators (general); mortality indicators (motor vehicle); mortality indicators (other); hospital data-based (overall); hospital data-based (traumatic brain injury (TBI)); long-term disability (overall). Following two work group discussions and after drafting and revising indicator specifications, agreement was reached on mortality indicators and specifications. Specifications for those mortality indicators are presented. Morbidity indicators are still to be agreed. RESULTS: The mortality indicators proposed were age-adjusted rates of injury death; motor vehicle traffic crash-related death; self-harm/suicide; assault/homicide; and TBI death. The empirical work highlighted difficulties in identifying TBI in countries where mortality data do not capture multiple injuries, prompting us to drop the mortality indicator related to TBI and moving us instead to introduce an indicator to monitor the use of undetermined intent in the classification of injury mortality. CONCLUSION: The ICE has reached a consensus on what injury mortality indicators should be used for comparison between countries. Specifications for each of these have been applied successfully to the mortality data of seven countries.

An investigation into methods to develop indicators to measure injury related impairment.

OBJECTIVE: To investigate whether valid indicators of injury-related impairment could be developed based on data from a New Zealand national no-fault accident insurance scheme. DESIGN: The feasibility of (1) developing impairment related indicators using insurance data directly, and (2) deriving diagnosis specific probability of impairment measures based on hospital discharge data were investigated. SETTING: The source data were lump sum payment data for permanent impairment arising from an injury event between 1 April 2002 and 31 October 2006, and hospital discharge data for injury events between 1 April 2002 and 31 December 2005. MAIN OUTCOME MEASURE: A threat of impairment measure was developed that was based on a list of International Classification of Diseases codes (version 10) which, if assessed would attract a lump sum payment for permanent impairment, and would almost always be expected to be admitted to hospital. RESULTS: A group of approximately 80 diagnoses satisfying the above criteria were identified. The trend in age standardised injury rates for the threat of impairment indicator is consistent with the trend for the New Zealand threat to life indicator. CONCLUSIONS: This work has provided a method for the development of hospital discharge-based serious threat of impairment injury indicators. This is an important first step in developing a comprehensive package of (threat of) disability indicators.

Assessing the validity of potential alcohol-related non-fatal injury indicators.

AIM: To assess critically the face validity of the World Health Organization's (WHO's) International Guide for Monitoring Alcohol Consumption and Related Harm (MACRH) for deriving indicators, for the purposes of developing non-fatal alcohol-related injury indicators in New Zealand. DESIGN: MACRH's five solutions for deriving indicators are: (i) use only alcohol-specific cases; (ii) identify subsets of events known to be highly alcohol-related; (iii) utilize control indicators that are rarely alcohol-related; (iv) estimate alcohol attributable fractions (AAFs) and adjust indicators accordingly; and (v) develop composite indicators. These were assessed in terms of their face validity with particular reference to New Zealand. FINDINGS: There are significant face validity issues with each of the five options. Solution 4 offers the greatest promise, provided that: (i) valid AAFs can be derived and they are updated regularly; and (ii) appropriate adjustment is made for extraneous influences on the estimates of alcohol-related harm. To date, the latter has not been carried out. CONCLUSIONS: Most potential sources of data on alcohol-related harm are subject to extraneous influences, which vary over time and space. While the attempt by WHO to offer solutions to this problem is laudable, the solutions do not address the problem adequately. MACRH guidelines need to be revised to include criteria for a valid outcome indicator.

NZ Government's trend analysis of hospitalised self-harm is misleading.

OBJECTIVE: The aim of this paper is to demonstrate that the trends published in the New Zealand (NZ) Government's 2006 Suicide Trends document for hospitalised self-harm are misleading. METHODS: Analysis of incident self-harm events resulting in hospitalisation and reference to published material on injury outcome indicators for the NZ Injury Prevention Strategy (NZIPS). RESULTS: The significant increase in rates of self-harm hospitalisation presented in Suicide Trends from 1989 to a large extent reflect changes in recording practice rather than any change in self-harm in the community. Indicators with significantly fewer threats to validity suggest there has been little, if any, increase in the incidence of self-harm. The authors of Suicide Trends did not adequately specify how they defined a case and, moreover, their methods were not consistent with those used for the NZIPS indicators. CONCLUSIONS AND IMPLICATIONS: The methodological challenges to producing valid indicators for the purposes of measuring trends in important non-fatal injury are substantial. Unless we accept that the usual methods of measuring trends in non-fatal injury are misleading and commit to taking up the challenge to produce and use better indicators, we will continue to run the risk of misleading ourselves and the public.

An analysis of the spatial arrangement of the myocardial aggregates making up the wall of the left ventricle.

OBJECTIVE: We used the technique of peeling of myocardial aggregates, usually described as 'fibres', to determine the spatial arrangement of the myocytes in the left ventricular wall of a healthy autopsied human heart. METHODS: We digitised the left ventricular outer and inner boundaries, as well as the pathways in space, of almost 3000 aggregates harvested from the left ventricular myocardium. During the process of gradual peeling, we sought to identify the myocardial aggregates as uniformly as possible. Despite this, interpolation was necessary to complete the pattern so as to construct a unit vector field that represented the preferred direction of the myocardial aggregates throughout the entirety of the walls of the left ventricle of this individual human heart. RESULTS: Apart from the overall systematic arrangement of the aggregates necessary to achieve physiologic ventricular contraction, we documented substantial local heterogeneities in the orientation of the myocardial aggregates. In particular, a significant proportion of aggregates was found to intrude obliquely with respect to the ventricular boundaries, with markedly heterogeneous distribution. Moreover, the distribution of the helical angle of the aggregates relative to the ventricular base varied notably throughout the left ventricular free walls and the septum. Within the generally quite uniform and continuous structure of the ventricular mass, we were, however, unable to identify any organised tracts or functional subunits such as a 'helical ventricular band', nor did we find radial fibrous lamellas coursing across the ventricular wall. CONCLUSION: We suggest that the impact of local anatomical inhomogeneities, associated with gradients in regional contractile function on global ventricular dynamics, has been systematically underestimated in the past. Our analysis confirms furthermore the continuous nature of the myocardium associated with an overall gross organisation of the fibre direction field; however, there is no evidence of substructures compartmentalising the ventricles.

Beta-blockade at low doses restoring the physiological balance in myocytic antagonism.

OBJECTIVE: The ventricular mass is organized in the form of meshwork, with populations of myocytes aggregated in a supporting matrix of fibrous tissue, with some myocytes aligned obliquely across the wall so as to work in an antagonistic fashion compared to the majority of myocytes, which are aggregated together in tangential alignment. Prompted by results from animal experiments, which showed a disparate response of the two populations of aggregated myocytes to negative inotropic medication, we sought to establish whether those myocytes that aggregated so as to extend obliquely across the thickness of the ventricular walls are more sensitive to beta-blockade than the prevailing population in which the myocytes are aggregated together with tangential alignment. If the two populations respond in similar differing fashion in the clinical situation, we hypothesize that this might help to explain why drugs blocking the beta-receptors improve function of the ventricular pump in the setting of congestive cardiac failure. METHODS: We implanted needle probes in 13 patients studied during open heart surgery, measuring the forces generated in the ventricular wall and seeking to couple the probes either to myocytes aggregated together with tangential alignment or to those aggregated in oblique fashion across the ventricular walls. In a first series of patients, we injected probatory doses intravenously, amounting to a total bolus of 40-100mg Esmolol, while in a second series, we gave fixed yet rising doses of 5, 10, and 20mg Esmolol in three separate boluses. RESULTS: Forces recorded in the aggregated myocytes with tangential alignment decreased insignificantly upon administration of low doses (57.1+/-12.4 mN-->56.6+/-7.6 mN), while forces recorded in the myocytes aggregated obliquely across the ventricular wall showed a significant decrease in the mean (59.3+/-11.6 mN-->47.4+/-6.4 mN). CONCLUSIONS: The markedly disparate action of drugs blocking beta-receptors at low dosage seems to be related to the heterogeneous extent, and time course, of systolic loading of the myocytes. This, in turn, depends on whether the myocytes themselves are aggregated together with tangential or oblique alignments relative to the thickness of the ventricular walls.

Three-dimensional architecture of the left ventricular myocardium.

Concepts for ventricular function tend to assume that the majority of the myocardial cells are aligned with their long axes parallel to the epicardial ventricular surface. We aimed to validate the existence of aggregates of myocardial cells orientated with their long axis intruding obliquely between the ventricular epicardial and endocardial surfaces and to quantitate their amount and angulation. To compensate for the changing angle of the long axis of the myocytes relative to the equatorial plane of the ventricles with varying depths within the ventricular walls, the so-called helical angle, we used pairs of cylindrical knives of different diameters to punch semicircular slices from the left ventricular wall of pigs, the slices extending from the epicardium to the endocardium. The slices were pinned flat, fixed in formaldehyde, embedded in paraffin, sectioned, stained with azan or hematoxilin and eosin, and analyzed by a new semiautomatic procedure. We made use of new techniques in informatics to determine the number and angulation of the aggregates of myocardial cells cut in their long axis. The alignment of the myocytes cut longitudinally varied markedly between the epicardium and the endocardium. Populations of myocytes, arranged in strands, diverge by varying angles from the epicardial surface. When paired knives of decreasing diameter were used to cut the slices, the inclination of the diagonal created by the arrays increases, while the lengths of the array of cells cut axially decreases. The visualization of the size, shape, and alignment of the myocytic arrays at any side of the ventricular wall is determined by the radius of the knives used, the range of helical angles subtended by the alignment of the myocytes throughout the thickness of the wall, and their angulation relative to the epicardial surface. Far from the majority of the ventricular myocytes being aligned at angles more or less tangential to the epicardial lining, we found that three-fifths of the myocardial cells had their long axes diverging at angles between 7.5 and 37.5 degrees from an alignment parallel to the epicardium. This arrangement, with the individual myocytes supported by connective tissue, might control the cyclic rearrangement of the myocardial fibers. This could serve as an important control of both ventricular mural thickening and intracavitary shape.

The myocardium and its fibrous matrix working in concert as a spatially netted mesh: a critical review of the purported tertiary structure of the ventricular mass.

With the increasing interest now paid to volume reduction surgery, in which the cardiac surgeon is required to resect the ventricular myocardium to an extent unenvisaged in the previous century, it is imperative that we develop as precise knowledge as is possible of the basic structure of the ventricular myocardial mass and its functional correlates. This is the most important in the light of the adoption by some cardiac surgeons of an unvalidated model which hypothesises that the entire myocardial mass can be unravelled to produce one continuous band. It is our opinion that this model, and the phylogenetic and functional correlates derived from it, is incompatible with current concepts of cardiac structure and cardiodynamics. Furthermore, the proponents of the continuous myocardial band have made no effort to demonstrate perceived deficiencies with current concepts, nor have they performed any histological studies to validate their model. Clinical results using modifications of radius reduction surgery based on the concept of the continuous myocardial band show that the procedure essentially becomes ineffective. As we show in this review, if we understand the situation correctly, it was the erstwhile intention of the promoters of the continuous band to elucidate the basic mechanism of diastolic ventricular dilation. Their attempts, however, are doomed to failure, as is any attempt to conceptualise the myocardial mass on the basis of a tertiary structure, because of the underlying three-dimensional netting of the myocardial aggregates and the supporting fibrous tissue to form the myocardial syncytium. Thus, the ventricular myocardium is arranged in the form of a modified blood vessel rather than a skeletal muscle. If an analogy is required with skeletal muscle, then the ventricular myocardium possesses the freedom of motion, and the ability for shaping and conformational self-controlling that is better seen in the tongue. It is part of this ability that contributes to the rapid end-systolic ventricular dilation. Histologic investigations reveal that the fibrous content of the three-dimensional mesh is relatively inhomogeneous through the ventricular walls, particularly when the myocardium is diseased. The regional capacity to control systolic mural thickening, therefore, varies throughout the walls of the ventricular components. The existence of the spatially netted structure of the ventricular mass, therefore, must invalidate any attempt to conceptualise the ventricular myocardium as a tertiary arrangement of individual myocardial bands or tracts.