Patients' and physicians' beliefs and attitudes towards integrating personalized risk estimates into patient education about left ventricular assist device therapy

BACKGROUND

Personalized risk (PR) estimates may enhance clinical decision making and risk communication by providing individualized estimates of patient outcomes. We explored stakeholder attitudes toward the utility, acceptability, usefulness and best-practices for integrating PR estimates into patient education and decision making about Left Ventricular Assist Device (LVAD).

METHODS AND RESULTS

As part of a 5-year multi-institutional AHRQ project, we conducted 40 interviews with stakeholders (physicians, nurse coordinators, patients, and caregivers), analyzed using Thematic Content Analysis. All stakeholder groups voiced positive views towards integrating PR in decision making. Patients, caregivers and coordinators emphasized that PR can help to better understand a patient's condition and risks, prepare mentally and logistically for likely outcomes, and meaningfully engage in decision making. Physicians felt it can improve their decision making by enhancing insight into outcomes, enhance tailored pre-emptive care, increase confidence in decisions, and reduce bias and subjectivity. All stakeholder groups also raised concerns about accuracy, representativeness and relevance of algorithms; predictive uncertainty; utility in relation to physician's expertise; potential negative reactions among patients; and overreliance.

CONCLUSION

Stakeholders are optimistic about integrating PR into clinical decision making, but acceptability depends on prospectively demonstrating accuracy, relevance and evidence that benefits of PR outweigh potential negative impacts on decision making quality.

SKey Concepts Surrounding Cardiogenic Shock

Cardiogenic shock (CS) is the final common pathway of impaired cardiovascular performance that results in ineffective forward cardiac output producing clinical and biochemical signs of organ hypoperfusion. CS represents the most common cause of shock in the cardiac intensive care unit (CICU) and accounts for a substantial proportion of CICU patient deaths. Despite significant advances in revascularization techniques, pharmacologic therapeutics and mechanical support devices, CS remains associated with a high mortality rate. Indeed, the prevalence of CS within the CICU appears to be increasing. CS can be differentiated as phenotypes reflecting different metabolic, inflammatory, and hemodynamic profiles, depending also on anatomic substrate and congestion profile. Future prospective studies and clinical trials may further characterize these phenotypes and apply targeted intervention for each phenotype and SCAI SHOCK stage rather than a one-size-fits-all approach. Overall, there are 8 key concepts of CS; 1) the mortality associated with CS; 2) Shock attributed to AMI may be declining in both incidence and associated mortality; 3) providers should think about hemodynamic, metabolic, inflammation and cardiac function in totality to assess CS; 4) CS is a dynamic process; 5) no randomized trials evaluating use of the PAC in patients with CS; 6) most data supporting neosynephrine as first line agent in CS; 7) most registries suggest that almost half of CS patients do not have any mechanical support, and the vast majority of the remainder utilize the IABP; and 8) patients with AMI CS should receive emergent PCI of the culprit vessel.

Left Ventricular Unloading during Extracorporeal Life Support: Current Practice

Veno-arterial extracorporeal life support (VA-ECLS) is a powerful tool that can provide complete cardiopulmonary support for patients with refractory cardiogenic shock. However, VA-ECLS increases left ventricular afterload resulting in greater myocardial oxygen demand, which can impair myocardial recovery and worsen pulmonary edema. These complications can be ameliorated by various LV venting strategies to unload the LV. Evidence suggests that LV venting improves outcomes in VA-ECLS, but there is a paucity of randomized trials to help guide optimal strategy and the timing of venting. In this review, we discuss the available evidence regarding LV venting in VA-ECLS, explain important hemodynamic principles involved, and propose a practical approach to LV venting in VA-ECLS.

A principal components analysis of factors associated with successful implementation of an LVAD decision support tool

BACKGROUND

A central goal among researchers and policy makers seeking to implement clinical interventions is to identify key facilitators and barriers that contribute to implementation success. Despite calls from a number of scholars, empirical insights into the complex structural and cultural predictors of why decision aids (DAs) become routinely embedded in health care settings remains limited and highly variable across implementation contexts.

METHODS

We examined associations between "reach", a widely used indicator (from the RE-AIM model) of implementation success, and multi-level site characteristics of nine LVAD clinics engaged over 18 months in implementation and dissemination of a decision aid for left ventricular assist device (LVAD) treatment. Based on data collected from nurse coordinators, we explored factors at the level of the organization (e.g. patient volume), patient population (e.g. health literacy; average sickness level), clinician characteristics (e.g. attitudes towards decision aid; readiness for change) and process (how the aid was administered). We generated descriptive statistics for each site and calculated zero-order correlations (Pearson's r) between all multi-level site variables including cumulative reach at 12 months and 18 months for all sites. We used principal components analysis (PCA) to examine any latent factors governing relationships between and among all site characteristics, including reach.

RESULTS

We observed strongest inclines in reach of our decision aid across the first year, with uptake fluctuating over the second year. Average reach across sites was 63% (s.d. = 19.56) at 12 months and 66% (s.d. = 19.39) at 18 months. Our PCA revealed that site characteristics positively associated with reach on two distinct dimensions, including a first dimension reflecting greater organizational infrastructure and standardization (characteristic of larger, more established clinics) and a second dimension reflecting positive attitudinal orientations, specifically, openness and capacity to give and receive decision support among coordinators and patients.

CONCLUSIONS

Successful implementation plans should incorporate specific efforts to promote supportive and mutually informative interactions between clinical staff members and to institute systematic and standardized protocols to enhance the availability, convenience and salience of intervention tool in routine practice. Further research is needed to understand whether "core predictors" of success vary across different intervention types.

Empagliflozin Effects on Pulmonary Artery Pressure in Patients With Heart Failure: Results From the EMBRACE-HF Trial

BACKGROUND

Sodium glucose cotransporter 2 inhibitors (SGLT2 inhibitors) prevent heart failure (HF) hospitalizations in patients with type 2 diabetes and improve outcomes in those with HF and reduced ejection fraction, regardless of type 2 diabetes. Mechanisms of HF benefits remain unclear, and the effects of SGLT2 inhibitor on hemodynamics (filling pressures) are not known. The EMBRACE-HF trial (Empagliflozin Evaluation by Measuring Impact on Hemodynamics in Patients With Heart Failure) was designed to address this knowledge gap.

METHODS

EMBRACE-HF is an investigator-initiated, randomized, multicenter, double-blind, placebo-controlled trial. From July 2017 to November 2019, patients with HF (regardless of ejection fraction, with or without type 2 diabetes) and previously implanted pulmonary artery (PA) pressure sensor (CardioMEMS) were randomized across 10 US centers to empagliflozin 10 mg daily or placebo and treated for 12 weeks. The primary end point was change in PA diastolic pressure (PADP) from baseline to end of treatment (average PADP weeks 8-12). Secondary end points included health status (Kansas City Cardiomyopathy Questionnaire score), natriuretic peptides, and 6-min walking distance.

RESULTS

Overall, 93 patients were screened, and 65 were randomized (33 to empagliflozin, 32 to placebo). The mean age was 66 years; 63% were male; 52% had type 2 diabetes; 54% were in New York Heart Association class III/IV; mean ejection fraction was 44%; median NT-proBNP (N-terminal pro B-type natriuretic peptide) was 637 pg/mL; and mean PADP was 22 mm Hg. Empagliflozin significantly reduced PADP, with effects that began at week 1 and amplified over time; average PADP (weeks 8-12) was 1.5 mm Hg lower (95% CI, 0.2-2.8; P=0.02); and at week 12, PADP was 1.7 mm Hg lower (95% CI, 0.3-3.2; P=0.02) with empagliflozin versus placebo. Results were consistent for PA systolic and PA mean pressures. There was no difference in mean loop diuretic management (daily furosemide equivalents) between treatment groups. No significant differences between treatment groups were observed in Kansas City Cardiomyopathy Questionnaire scores, natriuretic peptide levels, and 6-min walking distance.

CONCLUSIONS

In patients with HF and CardioMEMS PA pressure sensor, empagliflozin produced rapid reductions in PA pressures that were amplified over time and appeared to be independent of loop diuretic management. Registration: URL: https://www.clinicaltrials.gov; Unique identifier: NCT03030222.

Survival on the Heart Transplant Waiting List

Importance

With continuing improvements in medical devices and more than a decade since the 2006 United Network for Organ Sharing (UNOS) allocation policy, it is pertinent to assess survival among patients on the heart transplantation waiting list, especially given the recently approved 2018 UNOS allocation policy.

Objectives

To assess survival outcomes among patients on the heart transplant waiting list during the past 3 decades and to examine the association of ventricular assist devices (VADs) and the 2006 UNOS allocation policy with survival.

Design, Setting, and Participants

A retrospective cross-sectional used the UNOS database to perform an analysis of 95 323 candidates wait-listed for heart transplantation between January 1, 1987, and December 29, 2017. Candidates for all types of combined transplants were excluded (n = 2087). Patients were followed up from the time of listing to death, transplantation, or removal from the list due to clinical improvement. Competing-risk, Kaplan-Meier, and multivariable Cox proportional hazards regression analyses were used.

Main Outcomes and Measures

The analysis involved an unadjusted and adjusted survival analysis in which the primary outcome was death on the waiting list. Because of changing waiting list preferences and policies during the study period, the intrinsic risk of death for wait-listed candidates was assessed by individually analyzing, comparing, and adjusting for several candidate risk factors.

Results

In total, 95 323 candidates (72 915 men [76.5%]; mean [SD] age, 51.9 [12.0] years) were studied. In the setting of changes in listing preferences, 1-year survival on the waiting list increased from 34.1% in 1987-1990 to 67.8% in 2011-2017 (difference in proportions, 0.34%; 95% CI, 0.32%-0.36%; P < .001). The 1-year waiting list survival for candidates with VADs increased from 10.2% in 1996-2000 to 70.0% in 2011-2017 (difference in proportions, 0.60%; 95% CI, 0.58%-0.62%; P < .001). Similarly, in the setting of changing mechanical circulatory support indications, the 1-year waiting list survival for patients without VADs increased from 53.9% in 1996-2000 to 66.5% in 2011-2017 (difference in proportions, 0.13%; 95% CI, 0.12%-0.14%; P < .001). In the decade prior to the 2006 UNOS allocation policy, the 1-year waiting list survival was 51.1%, while in the decade after it was 63.9% (difference in proportions, 0.13%; 95% CI, 0.12%-0.14%; P < .001). In adjusted analysis, each time period after 1987-1990 had a marked decrease in waiting list mortality.

Conclusions and Relevance

This study found temporally associated increases in heart transplant waiting list survival for all patient groups (with or without VADs, UNOS status 1 and status 2 candidates, and candidates with poor functional status).

Donor and transplant candidate selection for solid organ transplantation during the COVID-19 pandemic

Severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2), a novel coronavirus responsible for a worldwide pandemic has forced drastic changes in medical practice in an alarmingly short period of time. Caregivers must modify their strategies as well as optimize the utilization of resources to ensure public and patient safety. For organ transplantation, in particular, the loss of lifesaving organs for transplantation could lead to increased waitlist mortality. The priority is to select uninfected donors to transplant uninfected recipients while maintaining safety for health care systems in the backdrop of a virulent pandemic. We do not yet have a standard approach to evaluating donors and recipients with possible SARS-CoV-2 infection. Our current communication shares a protocol for donor and transplant recipient selection during the coronavirus disease 2019 (COVID-19) pandemic to continue lifesaving solid organ transplantation for heart, lung, liver, and kidney recipients. The initial results using this protocol are presented here and meant to encourage dialogue between providers, offering ideas to improve safety in solid organ transplantation with limited health care resources. This protocol was created utilizing the guidelines of various organizations and from the clinical experience of the authors and will continue to evolve as more is understood about SARS-CoV-2 and how it affects organ donors and transplant recipients.

Abstract TP392: Evaluation of the CHADS 2 , CHA 2 DS 2 -VASc, and R 2 CHADS 2 Risk Assessment Scores in Continuous Flow LVADs

Background: The development of stroke while on continuous flow left ventricular assist device (CF-LVAD) remains a source of significant morbidity and mortality. The ability to risk stratify these patients can improve postoperative management.

Objective: To describe the overall experience of cerebrovascular accidents in CF-LVAD patients at a large volume tertiary center and compare the utility of CHADS 2 , CHA 2 DS 2 -VASc, and R 2 CHADS 2 scores.

Methods: A retrospective analysis of 522 patients (524 CF-LVADs: HeartMate-II=402; Heartware=122), between 2003 and 2016, was conducted. Post-operative heparin for 2-3 days, warfarin (goal INR 2-3), and 80-325mg aspirin were administered daily. Cerebrovascular vascular accident (CVA) was defined as any focal or global deficit with positive imaging. The CHADS 2 , R 2 CHADS 2 and CHA 2 DS 2 -VASc scores were calculated. Baseline characteristics and risk assessment scores were compared between patients with ischemic CVA (ICVA) and no CVA (nCVA). Kaplan-Meier analysis was conducted.

Results: Mean age was 54.7±13.6 years, 21.8% were female and 44.8% had ischemic cardiomyopathy. Eighty patients (15.3%) had 98 events of ICVA. Median duration between implant and ICVA was 127 [range 1-2226] days. Hemorrhagic conversion occurred in 9 (9.2%) patients. The CHADS 2 (ICVA=2.4±1.0, nCVA=2.3±1.1, p-value=0.53), CHA 2 DS 2 -VASc (ICVA=3.2±1.3, nCVA=2.9±1.3, p-value=0.08) and R 2 CHADS 2 (ICVA=3.5±1.5, nCVA=3.2±1.6, p-value=0.22) were all higher for ICVA cohort. Patients with multiple ICVAs had a mean CHADS 2 score of 2.5±0.74, CHA 2 DS 2 -VASc score of 3.5±1.1, and R 2 CHADS 2 score of 4±1.2. Freedom from stroke was significantly lower in the CHA 2 DS 2 -VASc ≥3 compared to the CHA 2 DS 2 -VASc <3 [Figure: Kaplan-Meier log-rank p-value=0.009].

Conclusion: CHA 2 DS 2 -VASc of ≥3 was associated with ICVA in this cohort of CF-LVAD patients. Specifically tailored risk-scores are needed to better predict those at risk for neurological events in CF-LVADs

Outcomes of pre-emptive and rescue use of percutaneous left ventricular assist device in patients with structural heart disease undergoing catheter ablation of ventricular tachycardia

PURPOSE

Patient selection and timing of percutaneous left ventricular assist device (pLVAD) insertion for maximal benefit during ventricular tachycardia (VT) ablation is not well defined. We aimed to assess the outcomes of pre-emptive and rescue use of pLVAD during VT ablation in patients with ischemic and non-ischemic cardiomyopathy.

METHODS

Between January 2009 and October 2011, 93 patients underwent VT ablation. Three groups were compared: (1) Rescue group (n = 12)-patients who required emergent pLVAD insertion due to hemodynamic collapse during VT ablation, (2) Pre-emptive group (n = 24)-patients who had pre-ablation pLVAD insertion, and (3) Non-pLVAD group (n = 57)-patients who did not undergo pLVAD insertion. Procedural outcomes including 30-day mortality were compared.

RESULTS

Thirty-day mortality was higher in the Rescue group compared to the Pre-emptive group (58 vs. 4 %, p = 0.003) and non-pLVAD (58 vs. 3 %, p = 0.001) group. There was no significant difference in 30-day mortality or long-term freedom of VT between the pre-emptive and non-pLVAD groups.

CONCLUSIONS

Despite rescue pLVAD insertion, hemodynamic collapse during VT ablation is associated with a persistently high 30-day mortality. Further studies are warranted to predict hemodynamic collapse and to refine the role of pLVAD in this setting.

Association between cell-derived microparticles and adverse events in patients with nonpulsatile left ventricular assist devices

BACKGROUND

Continuous-flow left ventricular assist devices (LVADs) expose blood cells to high shear stress, potentially resulting in the production of microparticles that express phosphatidylserine (PS+) and promote coagulation and inflammation. In this prospective study, we attempted to determine whether PS+ microparticle levels correlate with clinical outcomes in LVAD-supported patients.

METHODS

We enrolled 20 patients undergoing implantation of the HeartMate II LVAD (Thoratec Corp, Pleasanton, CA) and 10 healthy controls who provided reference values for the microparticle assays. Plasma was collected before LVAD implantation, at discharge, at the 3-month follow-up, and when an adverse clinical event occurred. We quantified PS+ microparticles in the plasma using flow cytometry.

RESULTS

During the study period, 8 patients developed adverse clinical events: ventricular tachycardia storm in 1, non-ST-elevation myocardial infarction in 2, arterial thrombosis in 2, gastrointestinal bleeding in 2, and stroke in 3. Levels of PS+ microparticles were higher in patients at baseline than in healthy controls (2.11% ± 1.26% vs 0.69% ± 0.46%, p = 0.007). After LVAD implantation, patient PS+ microparticle levels increased to 2.39% ± 1.22% at discharge and then leveled to 1.97% ± 1.25% at the 3-month follow-up. Importantly, levels of PS+ microparticles were significantly higher in patients who developed an adverse event than in patients with no events (3.82% ± 1.17% vs 1.57% ± 0.59%, p < 0.001), even though the 2 patient groups did not markedly differ in other clinical and hematologic parameters.

CONCLUSIONS

Our results suggest that an elevation of PS+ microparticle levels may be associated with adverse clinical events. Thus, measuring PS+ microparticle levels in LVAD-supported patients may help identify patients at increased risk for adverse events.

A prospective feasibility trial investigating the use of the Impella 2.5 system in patients undergoing high-risk percutaneous coronary intervention (The PROTECT I Trial): initial U.S. experience

OBJECTIVES

We sought to evaluate the safety and feasibility of the Impella 2.5 system (Abiomed Inc., Danvers, Massachusetts) in patients undergoing high-risk percutaneous coronary intervention (PCI).

BACKGROUND

The Impella 2.5 is a miniaturized percutaneous cardiac assist device, which provides up to 2.5 l/min forward flow from the left ventricle into the systemic circulation.

METHODS

In a prospective, multicenter study, 20 patients underwent high-risk PCI with minimally invasive circulatory support employing the Impella 2.5 system. All patients had poor left ventricular function (ejection fraction <or=35%) and underwent PCI on an unprotected left main coronary artery or last patent coronary conduit. Patients with recent ST-segment elevation myocardial infarction or cardiogenic shock were excluded. The primary safety end point was the incidence of major adverse cardiac events at 30 days. The primary efficacy end point was freedom from hemodynamic compromise during PCI (defined as a decrease in mean arterial pressure below 60 mm Hg for >10 min).

RESULTS

The Impella 2.5 device was implanted successfully in all patients. The mean duration of circulatory support was 1.7 +/- 0.6 h (range: 0.4 to 2.5 h). Mean pump flow during PCI was 2.2 +/- 0.3 l/min. At 30 days, the incidence of major adverse cardiac events was 20% (2 patients had a periprocedural myocardial infarction; 2 patients died at days 12 and 14). There was no evidence of aortic valve injury, cardiac perforation, or limb ischemia. Two patients (10%) developed mild, transient hemolysis without clinical sequelae. None of the patients developed hemodynamic compromise during PCI.

CONCLUSIONS

The Impella 2.5 system is safe, easy to implant, and provides excellent hemodynamic support during high-risk PCI. (The PROTECT I Trial; NCT00534859).

Use of the TandemHeart Percutaneous Ventricular Assist Device to Support Patients Undergoing High-Risk Percutaneous Coronary Intervention

OBJECTIVES: We describe our experience in using the TandemHeart percutaneous ventricular assist device (pVAD) during high-risk percutaneous coronary intervention (PCI). BACKGROUND: Coronary artery bypass grafting (CABG) is the preferred treatment for disease in an unprotected left main coronary artery or left main equivalent. However, severe comorbidities may preclude surgery in some patients. In these cases, PCI is also often a high-risk procedure. The pVAD is designed to provide circulatory support during high-risk PCI. METHODS AND RESULTS: We used the pVAD for hemodynamic support during PCI in 5 consecutive patients who were ineligible for CABG because of severe comorbidities. In all 5 cases, the device was inserted and support initiated without complications. Percutaneous revascularization was successfully performed with pVAD support (approximately 3 L/minute). Four patients were supported for an average of 107 minutes, the pVAD being withdrawn shortly after PCI; all 4 patients recovered uneventfully. The fifth patient required support for 48 more hours after the procedure because of poor ventricular function. He died of heart failure and severe mitral regurgitation 10 days after pVAD withdrawal. CONCLUSIONS: The pVAD may provide sufficient circulatory support for hemodynamic protection during high-risk PCI, thus improving morbidity and mortality and broadening the therapeutic options for high-risk patients. Further investigation of this device is warranted.

Use of the TandemHeart percutaneous ventricular assist device to support patients undergoing high-risk percutaneous coronary intervention

OBJECTIVES

We describe our experience in using the TandemHeart percutaneous ventricular assist device (pVAD) during high-risk percutaneous coronary intervention (PCI).

BACKGROUND

Coronary artery bypass grafting (CABG) is the preferred treatment for disease in an unprotected left main coronary artery or left main equivalent. However, severe comorbidities may preclude surgery in some patients. In these cases, PCI is also often a high-risk procedure. The pVAD is designed to provide circulatory support during high-risk PCI.

METHODS AND RESULTS

We used the pVAD for hemodynamic support during PCI in 5 consecutive patients who were ineligible for CABG because of severe comorbidities. In all 5 cases, the device was inserted and support initiated without complications. Percutaneous revascularization was successfully performed with pVAD support (approximately 3 L per minute). Four patients were supported for an average of 107 minutes, the pVAD being withdrawn shortly after PCI; all 4 patients recovered uneventfully. The fifth patient required support for 48 more hours after the procedure because of poor ventricular function. He died of heart failure and severe mitral regurgitation 10 days after pVAD withdrawal.

CONCLUSIONS

The pVAD may provide sufficient circulatory support for hemodynamic protection during high-risk PCI, thus improving morbidity and mortality and broadening the therapeutic options for high-risk patients. Further investigation of this device is warranted.

Termination of DNA synthesis by novel 3'-modified-deoxyribonucleoside 5'-triphosphates

Eight 3'-modified-dNTPs were synthesized and tested in two different DNA template assays for incorporation activity. From this enzymatic screen, two 3'-O-methyl-dNTPs were shown to terminate DNA syntheses mediated by a number of polymerases and may be used as alternative terminators in Sanger sequencing. 3'-O-(2-Nitrobenzyl)-dATP is a UV sensitive nucleotide and was shown to be incorporated by several thermostable DNA polymerases. Base specific termination and efficient photolytic removal of the 3'-protecting group was demonstrated. Following deprotection, DNA synthesis was reinitiated by the incorporation of natural nucleotides into DNA. The identification of this labile terminator and the demonstration of a one cycle stop-start DNA synthesis are initial steps in the development of a novel sequencing strategy.

DNA typing and genetic mapping with trimeric and tetrameric tandem repeats

Tandemly reiterated sequences represent a rich source of highly polymorphic markers for genetic linkage, mapping, and personal identification. Human trimeric and tetrameric short tandem repeats (STRs) were studied for informativeness, frequency, distribution, and suitability for DNA typing and genetic mapping. The STRs were highly polymorphic and inherited stably. A STR-based multiplex PCR for personal identification is described. It features fluorescent detection of amplified products on sequencing gels, specific allele identification, simultaneous detection of independent loci, and internal size standards. Variation in allele frequencies were explored for four U.S. populations. The three STR loci (chromosomes 4, 11, and X) used in the fluorescent multiplex PCR have a combined average individualization potential of 1/500 individuals. STR loci appear common, being found every 300-500 kb on the X chromosome. The combined frequency of polymorphic trimeric and tetrameric STRs could be as high as 1 locus/20 kb. The markers should be useful for genetic mapping, as they are sequence based, and can be multiplexed with the PCR. A method enabling rapid localization of STRs and determination of their flanking DNA sequences was developed, thus simplifying the identification of polymorphic STR loci. The ease by which STRs may be identified, as well as their genetic and physical mapping utility, give them the properties of useful sequence tagged sites (STSs) for the human genome initiative.

Automated DNA sequencing of the human HPRT locus

The complete sequence of 57 kb of the human HPRT locus has been determined using automated fluorescent DNA sequencing. The strategy employed increasingly directed sequencing methods: A randomly generated M13 library was sequenced to generate contiguous overlapping sets of sequences (contigs). M13 clones at the ends of these contigs were further sequenced using M13 (universal and reverse) and custom oligonucleotide primers to order the contigs and to complete the sequencing project. The human HPRT sequence includes 1676 bp 5' and 15,238 bp 3' to exons 1 and 9, respectively. The sequence contains 49 representatives of the Alu repeat, along with several other types of repetitive sequences. The Alu sequences exhibit a biased orientation, with those sequences in the first half of the locus oriented in the minus direction relative to transcription of the gene (3'----5' = 77%, P less than 0.005) and those sequences in the latter half of the locus oriented randomly (5'----3' = 67%, P less than 0.5). The development and performance of the sequencing strategy and the features of the human HPRT gene are presented.