Left Ventricular Energy Model Predicts Adverse Events in Women With Suspected Myocardial Ischemia: Results From The NHLBI-Sponsored Women's Ischemia Syndrome Evaluation (WISE) Study

Even "WISE-R?"-an Update on the NHLBI-Sponsored Women's Ischemia Syndrome Evaluation

PURPOSE OF REVIEW

For over 20 years, the Women's Ischemia Syndrome Evaluation (WISE), a program sponsored by the National Heart, Lung, and Blood Institute, has explored diverse and important aspects of ischemic heart disease in women.

RECENT FINDINGS

Women with symptoms and signs of ischemia but no significant epicardial obstructive coronary artery disease (INOCA) were documented to be at elevated risk for recurrent angina hospitalization, major adverse cardiac events, death, and health resource consumption rivaling those with obstructive coronary disease. WISE investigators have advanced our understanding of cardiovascular outcomes, systemic manifestations, psychological variables, socioeconomic factors, genetic contributions, hormonal status, advanced imaging, coronary functional findings, biomarkers, patient-reported outcomes, and treatments pertaining to women with this disease entity. This review delves into the WISE findings subsequent to a prior review1, postulates directions for future research, and asks are we "Even 'WISE-R?'".

Increased Hemoglobin Oxygen Affinity With 5-Hydroxymethylfurfural Supports Cardiac Function During Severe Hypoxia

Acclimatization to hypoxia or high altitude involves physiological adaptation processes, to influence oxygen (O2) transport and utilization. Several natural products, including aromatic aldehydes and isothiocyanates stabilize the R-state of hemoglobin (Hb), increasing Hb-O2 affinity and Hb-O2 saturation. These products are a counter intuitive therapeutic strategy to increase O2 delivery during hypoxia. 5-Hydroxymethylfurfural (5-HMF) is well known Amadori compound formed during the Maillard reaction (the non-enzymatic browning and caramelization of carbohydrate-containing foods after thermal treatment), with well documented effects in Hb-O2 affinity. This study explores the therapeutic potential of 5-HMF on left ventricular (LV) cardiac function (LVCF) during hypoxia. Anesthetized Golden Syrian hamsters received 5-HMF i.v., at 100 mg/kg and were subjected to stepwise increased hypoxia (15, 10, and 5%) every 30 min. LVCF was assessed using a closed chest method with a miniaturized conductance catheter via continuous LV pressure-volume (PV) measurements. Heart hypoxic areas were studied using pimonidazole staining. 5-HMF improved cardiac indices, including stroke volume (SV), cardiac output (CO), ejection fraction (EF), and stroke work (SW) compared to the vehicle group. At 5% O2, SV, CO, EF, and SW were increased by 53, 42, 33, and 51% with 5-HMF relative to vehicle. Heart chronotropic activity was not statistically changed, suggesting that differences in LV-CF during hypoxia by 5-HMF were driven by volume dependent effects. Analysis of coronary blood flow and cardiac muscle metabolism suggest no direct pharmacological effects from 5-HMF, therefore these results can be attributed to 5-HMF-dependent increase in Hb-O2 affinity. These studies establish that naturally occurring aromatic aldehydes, such as 5-HMF, produce modification of hemoglobin oxygen affinity with promising therapeutic potential to increase O2 delivery during hypoxic hypoxia.

Cardiac function during resuscitation from hemorrhagic shock with polymerized bovine hemoglobin-based oxygen therapeutic

Hemorrhage impairs myocardial contractile function and decreases oxygen delivery. This study investigates how polymerized bovine hemoglobin (PolyHb) solutions affect cardiac function after resuscitation from hemorrhagic shock (HS). Hamsters were hemorrhaged and resuscitated with PolyHb at 8.5 g/dL and 11.5 g/dL. Left ventricle (LV) function was assessed during shock and resuscitation using a miniaturize conductance catheter. PolyHb resuscitation had no beneficial effects in cardiac function; it increased cardiac afterload and systemic vascular resistance (SVR) of 46 and 116% for 8.5 and 11.5 g/dL, respectively. Study findings indicate that preclinical evaluation of cardiac function is essential to develop safe and efficacious alternatives to blood transfusion.

Predictive value of exercise myocardial perfusion imaging in the Medicare population: the impact of the ability to exercise

BACKGROUND

Although the prognostic value of quantitative single photon emission computed tomography myocardial perfusion imaging (MPI) with exercise and pharmacologic stress is well established, the prognostic and management value in the Medicare age population is less clear.

METHODS

The prospectively populated Cleveland Clinic nuclear cardiology database was used to identify 5,994 consecutive pateints, age >65 years [1,664 (28%) exercise MPI, mean age 72.4±5.1, 74% male], who underwent MPI between January 2004 and January 2008. Clinical baseline variables, post test 90 days revascularization and MPI variables were analyzed. Overall and stratified nonparametric survival estimates were obtained by Kaplan-Meier method. Median follow-up time was 2.4 years. Parametric hazard modeling with bootstrap bagging methods was used to determine prognostic variables predicting mortality.

RESULTS

There was no difference in mortality in patients with an abnormal MPI vs. those with normal MPI. Amongst the patients who underwent exercise MPI, there were 103 (6%) deaths and 121 (8.2%) revascularizations. Only lower exercise capacity (<7 METs) and higher end systolic volume (ESV) predicted mortality. Although a larger amount of ischemia influenced down stream revascularization ischemia, revascularization of patients with an abnormal exercise MPI did not offer a survival benefit (log rank P value=0.01).

CONCLUSIONS

In the a Medicare age population, exercise MPI perfusion variables influenced rates of revascularization but failed to provide incremental significant risk-stratification beyond exercise capacity. Maximum METs achieved appears to be a better predictor of survival.

The potential value of discordant studies

Many aspects of the clinical application of gated-single photon emission computed tomography (SPECT) have been well established by multiple trials and studies. However, its utility in the elderly (i.e., the Medicare population in the USA) remains unclear. This is an important population due to its rapid growth, coupled with the increasing prevalence of coronary artery disease with age. A paper in this issue, Predictive value of exercise myocardial perfusion imaging in the Medicare population: the impact of the ability to exercise, indicates that while gated-SPECT clearly directs the performance of interventions at the level of the coronary arteries in the elderly, outcomes are worse for those receiving an intervention vs. those receiving medical therapy. While some literature supports this observation, there are also well documented studies that indicate that the opposite is the case. As consumers of discordant studies, we find ourselves in the unenviable position of having to pull at the threads of evidence and follow them through in an attempt to reconcile the conflicting literature. This is reminiscent of the mythical Gregorian knot, a knot that was impossible to unravel by conventional means. However, it was "solved" by cutting it with a sword. In our case, the sword that we have is the removal of bias. It has been said that there are no unbiased studies, since we only measure what we believe and we tend to believe what we measure. This is further compounded in clinical practice since the Hippocratic Oath requires that the physician above all do no harm. Therefore it follows that whatever action is done is at least not detrimental to the patient. These are powerful belief systems that on the one hand allow us to rapidly discard "irrelevant" information and quickly get to the important point, but on the other hand they may inhibit us from seeing what is truly of value. Discordant and negative studies are important disruptors along the path to easy data assimilation, and force us to seek out sources of bias which otherwise may go unnoted. In the case of the above paper we might look past the perfusion data to the more important cardiac functional data which may contribute to changing the focus of diagnosis and treatment strategies, thus slicing through a little more of the knot.

A new cardiac variable identified?

Women with suspected cardiac syndrome X (CSX) are difficult to diagnosis and treat by conventional means. The women's ischemic syndrome evaluation (WISE) study, which started as an exploration of ischemic heart disease, increasingly focused on CSX, and two papers that represent an outgrowth and extension of this work are featured in this issue. Cardiovascular magnetic resonance imaging (CMRI) can generate a myocardial perfusion reserve index (MPRI) that is shown to be lower in women with CSX compared to normal controls. The MPRI is a ratio of resting to vasodilatation myocardial perfusion uptake and is relatively easy to measure. There is growing evidence that the CMRI measured MPRI provides unique information that should be regarded as a primary indicator of CSX disease severity. The papers describe the low levels of MPRI in a well documented CSX all female patient population. The context of this work and its relationship to other findings is discussed with an emphasis on the unique information that CMRI can provide.