David P. Daniels

Fractional Flow Reserve Assessment of Left Main Stenosis in the Presence of Downstream Coronary Stenoses

Background—Several studies have shown that fractional flow reserve (FFR) measurement can aid in the assessment of left main coronary stenosis. However, the impact of downstream epicardial stenosis on left main FFR assessment with the pressure wire in the nonstenosed downstream vessel remains unknown. Methods and Results—Variable stenoses were created in the left main coronary arteries and downstream epicardial vessels in 6 anaesthetized male sheep using balloon catheters. A total of 220 pairs of FFR assessments of the left main stenosis were obtained, before and after creation of a stenosis in a downstream epicardial vessel, by having a pressure-sensor wire in the other nonstenosed downstream vessel. The apparent left main FFR in the presence of downstream stenosis (FFRapp) was significantly higher compared with the true FFR in the absence of downstream stenosis (FFRtrue; 0.80±0.05 versus 0.76±0.05; estimate of the mean difference, 0.035; P<0.001). The difference between FFRtrue and FFRapp correlated with composite FFR of the left main plus stenosed artery (r=−0.31; P<0.001) indicating that this difference was greater with increasing epicardial stenosis severity. Among measurements with FFRapp >0.80, 9% were associated with an FFRtrue of <0.75. In all instances, the epicardial lesion was in the proximal portion of the stenosed vessel, and the epicardial FFR (combined FFR of the left main and downstream stenosed vessel) was ⩽0.50. Conclusions—A clinically relevant effect on the FFR assessment of left main disease with the pressure wire in a nonstenosed downstream vessel occurs only when the stenosis in the other vessel is proximal and very severe.

Calculation of the index of microcirculatory resistance without coronary wedge pressure measurement in the presence of epicardial stenosis

OBJECTIVES This study sought to investigate a novel method to calculate the index of microcirculatory resistance (IMR) in the presence of significant epicardial stenosis without the need for balloon dilation to measure the coronary wedge pressure (P(w)). BACKGROUND The IMR provides a quantitative measure of coronary microvasculature status. However, in the presence of significant epicardial stenosis, IMR calculation requires incorporation of the coronary fractional flow reserve (FFR(cor)), which requires balloon dilation within the coronary artery for P(w) measurement. METHODS A method to calculate IMR by estimating FFR(cor) from myocardial FFR (FFR(myo)), which does not require P(w) measurement, was developed from a derivation cohort of 50 patients from a single institution. This method to calculate IMR was then validated in a cohort of 72 patients from 2 other different institutions. Physiology measurements were obtained with a pressure-temperature sensor wire before coronary intervention in both cohorts. RESULTS From the derivation cohort, a strong linear relationship was found between FFR(cor) and FFR(myo) (FFR(cor) = 1.34 × FFR(myo) - 0.32, r(2) = 0.87, p < 0.001) by regression analysis. With this equation to estimate FFR(cor) in the validation cohort, there was no significant difference between IMR calculated from estimated FFR(cor) and measured FFR(cor) (21.2 ± 12.9 U vs. 20.4 ± 13.6 U, p = 0.161). There was good correlation (r = 0.93, p < 0.001) and agreement by Bland-Altman analysis between calculated and measured IMR. CONCLUSIONS The FFR(cor), and, by extension, microcirculatory resistance can be derived without the need for P(w). This method enables assessment of coronary microcirculatory status before or without balloon inflation, in the presence of epicardial stenosis.

Default neglect in attempts at social influence

Significance While a great deal is known about how people respond to influence tactics that are used on them, almost nothing is known about whether people understand these tactics and strategically use them to influence others. We examine whether people are successful at using the default effect, a widely studied bias with special policy relevance, to influence others’ choices. Overall, we find that managers, law/business/medical students, and US adults often fail to understand and/or use defaults, with some interesting exceptions. These findings suggest that the scope for improving social welfare via behavioral policy interventions is vast. Current theories suggest that people understand how to exploit common biases to influence others. However, these predictions have received little empirical attention. We consider a widely studied bias with special policy relevance: the default effect, which is the tendency to choose whichever option is the status quo. We asked participants (including managers, law/business/medical students, and US adults) to nudge others toward selecting a target option by choosing whether to present that target option as the default. In contrast to theoretical predictions, we find that people often fail to understand and/or use defaults to influence others, i.e., they show “default neglect.” First, in one-shot default-setting games, we find that only 50.8% of participants set the target option as the default across 11 samples (n = 2,844), consistent with people not systematically using defaults at all. Second, when participants have multiple opportunities for experience and feedback, they still do not systematically use defaults. Third, we investigate beliefs related to the default effect. People seem to anticipate some mechanisms that drive default effects, yet most people do not believe in the default effect on average, even in cases where they do use defaults. We discuss implications of default neglect for decision making, social influence, and evidence-based policy.

Impact Aversion in Arbitrator Decisions

An aversion to salient mistakes leads arbitrators to make mistakes more often, even where directives are clear, incentives strong, and post-hoc evaluation perfect. We study the choices of Major League Baseball umpires, who are directed to make binary decisions according to a single, objective criterion: pitch location. Using state-of-the-art pitch location technology, we examine over one million such decisions and find that every umpire in our sample distorts his directive by avoiding the option that would more strongly change the expected outcome of the game. This impact aversion is consistent with an avoidance of public scrutiny. Umpires face criticism from the public for mistakes that disrupt the course of the game; impact-averse umpires avoid scrutiny by avoiding game-changing options that could be mistaken.Do Major League Baseball umpires call balls and strikes solely in response to pitch location? We analyze all regular season calls from 2009 to 2011—over one million pitches—using non-parametric and structural estimation methods. We find that the strike zone contracts in 2-strike counts and expands in 3-ball counts, and that umpires are reluctant to call two strikes in a row. Effect sizes can be dramatic: in 2-strike counts the probability of a called strike drops by as much as 19 percentage points in the corners of the strike zone. We structurally estimate each umpires aversions to miscalling balls and his aversions to miscalling strikes in different game states. If an umpire is unbiased, he would only need to be 50% sure that a pitch is a strike in order to call a strike half the time. In fact, the average umpire needs to be 64% sure of a strike in order to call strike three half the time. Moreover, the least biased umpire still needs to be 55% sure of a strike in order to call strike three half the time. In other words, every umpire is biased. Contrary to their formal role as unbiased arbiters of balls and strikes, umpires are biased by the state of the at-bat when deciding whether a pitch intersects the strike zone.

Response to Letter Regarding Article, “Fractional Flow Reserve Assessment of Left Main Stenosis in the Presence of Downstream Coronary Stenoses”

We thank our colleagues Karabay et al for their interest and comments regarding our recent article entitled “Fractional Flow Reserve Assessment of Left Main Stenosis in the Presence of Downstream Coronary Stenoses.”1 They raise an important point about branch steal and how it may affect the pressure gradient in the presence of serial coronary stenoses. A recent in vitro study by our group demonstrated that the flow–pressure–resistance relationship in the setting of left main and downstream stenosis can be represented using a model of resistances.2 In the setting of a left main stenosis, let us consider the ostium of the left main artery as the inlet, with the …

Reply to Jung et al.: Default neglect persists over time and across contexts

We appreciate the comments and studies by Jung et al. (1). They test for default neglect in three new default games, finding that “Choice Architects” (CAs) are better than chance at correctly predicting the default effect in these new contexts. That said, we believe that Jung et al.’s claim that CAs are “excellent” at setting defaults (1) is premature. First, they do not present data on default-setting behavior, per se, but rather on beliefs about the default effect. This distinction is important because default-setting behavior does not always correlate with beliefs about the default effect (study 3 in ref. 2). Second, default neglect should be conceptualized as a spectrum from total … [↵][1]1To whom correspondence should be addressed. Email: jjzlatev{at}stanford.edu. [1]: #xref-corresp-1-1

Choice Architects Reveal a Bias Toward Positivity and Certainty

Biases can influence important decisions in social, political, and economic environments, but little is empirically known about whether and how individuals try to exploit others’ biases in strategic interactions. For instance, people must often decide between giving others choice sets with positive or certain options (likely influencing them toward safer options) versus negative or risky options (likely influencing them toward riskier options). In this paper, we study nudge strategies, strategic decisions about how to exploit others’ biases. We show that individuals’ nudge strategies are distorted towards presenting choice sets with positive or certain options, across nine experiments involving diverse samples (including business executives, law students, business students, medical students, and online adults) and multiple important contexts (including public policy, business, and medicine). In many cases, this distortion actually causes a majority of people to use a nudge strategy that backfires. Surprisingly, people’s predictions about the directional effects of nudge strategies are generally correct. Thus, simply prompting people to consider their own predictions can improve nudge strategies that would otherwise be suboptimal. The evidence is consistent with meta-prospect theory, in which properties familiar from prospect theory generate distortions in nudge strategies; for example, loss aversion generates a distortion towards presenting gain frames over presenting loss frames. Overall, our results suggest that improving well-intentioned but suboptimal nudge strategies is a feasible objective which could lead to substantial benefits for both individuals and society.Biases influence important decisions, but little is known about whether and how individuals try to exploit others’ biases in strategic interactions. Choice architects—that is, people who present choices to others—must often decide between presenting choice sets with positive or certain options (influencing others toward safer options) versus presenting choice sets with negative or risky options (influencing others toward riskier options). We show that choice architects’ influence strategies are distorted toward presenting choice sets with positive or certain options, across thirteen studies involving diverse samples (executives, law/business/medical students, adults) and contexts (public policy, business, medicine). These distortions appear to primarily reflect decision biases rather than social preferences, and they can cause choice architects to use influence strategies that backfire.