Abnormal longitudinal, base-to-apex myocardial perfusion gradient by quantitative blood flow measurements in patients with coronary risk factors

PET Myocardial Perfusion Imaging: Trends, Challenges, and Opportunities

Various non-invasive images are used in clinical practice for the diagnosis and prognostication of chronic coronary syndromes. Notably, quantitative myocardial perfusion imaging (MPI) through positron emission tomography (PET) has seen significant technical advancements and a substantial increase in its use over the past two decades. This progress has generated an unprecedented wealth of clinical information, which, when properly applied, can diagnose and fine-tune the management of patients with different types of ischemic syndromes. This state-of-art review focuses on quantitative PET MPI, its integration into clinical practice, and how it holds up at the eyes of modern cardiac imaging and revascularization clinical trials, along with future perspectives.

Mechanisms of left ventricular systolic dysfunction in light chain amyloidosis: a multiparametric cardiac MRI study

Background

Cardiac systolic dysfunction is a poor prognostic marker in light-chain (AL) cardiomyopathy, a primary interstitial disorder; however, its pathogenesis is poorly understood.

Purpose

This study aims to analyze the effects of extracellular volume (ECV) expansion, a surrogate marker of amyloid burden on myocardial blood flow (MBF), myocardial work efficiency (MWE), and left ventricular (LV) systolic dysfunction in AL amyloidosis.

Methods

Subjects with biopsy-proven AL amyloidosis were prospectively enrolled (April 2016-June 2021; Clinicaltrials.gov ID NCT02641145) and underwent cardiac magnetic resonance imaging (MRI) to quantify rest MBF by perfusion imaging, LV ejection fraction (LVEF) by cine MRI, and ECV by pre- and post-contrast T1 mapping. The MWE was estimated as external cardiac work from the stroke volume and mean arterial pressure normalized to the LV myocardial mass.

Results

Rest MBF in 92 subjects (62 ± 8 years, 52 men) with AL amyloidosis averaged 0.87 ± 0.21 ml/min/g and correlated with MWE (r = 0.42; p < 0.001). Rest MBF was similarly low in subjects with sustained hematologic remission after successful AL amyloidosis therapy (n = 21), as in those with recently diagnosed AL amyloidosis. Both MBF and MWE decreased by ECV tertile (p < 0.01 for linear trends). The association of ECV with MWE comprised a direct effect (84% of the total effect; p < 0.001) on MWE from adverse interstitial remodeling assessed by ECV and an indirect effect (16% of the total effect; p < 0.001) mediated by MBF. There was a significant base-to-apex gradient of rest MBF in subjects with higher amyloid burden.

Conclusions

In AL amyloidosis, both MBF and MWE decrease as cardiac amyloid burden and ECV expansion increase. Both structural and vascular changes from ECV expansion and myocardial amyloid burden appear to contribute to lower MWE.

Quantitative flow ratio derived pullback pressure gradient and CZT-SPECT measured longitudinal flow gradient for hemodynamically significant coronary artery disease

BACKGROUND

Whether physiological coronary diffuseness assessed by quantitative flow reserve (QFR) pullback pressure gradient (PPG) correlates with longitudinal myocardial blood flow (MBF) gradient and improves diagnostic performances for myocardial ischemia remains unknown.

METHODS AND RESULTS

MBF was measured in mL g-1 min-1 with 99mTc-MIBI CZT-SPECT at rest and stress, corresponding myocardial flow reserve (MFR = MBF stress/MBF rest) and relative flow reserve (RFR = MBF stenotic area/MBF reference) were calculated. Longitudinal MBF gradient was defined as apical and basal left ventricle MBF gradient. △longitudinal MBF gradient was calculated by longitudinal MBF gradient at stress and rest. QFR-PPG was acquired from virtual QFR pullback curve. QFR-PPG significantly correlated with hyperemic longitudinal MBF gradient (r = 0.45, P = 0.007) and △longitudinal MBF gradient (stress-rest) (r = 0.41, P = 0.016). Vessels with lower RFR had lower QFR-PPG (0.72 vs. 0.82, P = 0.002), hyperemic longitudinal MBF gradient (1.14 vs. 2.22, P = 0.003) and △longitudinal MBF gradient (0.50 vs. 1.02, P = 0.003). QFR-PPG, hyperemic longitudinal MBF gradient and △longitudinal MBF gradient showed comparable diagnostic performances for predicting decreased RFR (area under curve [AUC]: 0.82 vs. 0.81 vs. 0.75, P = NS) or QFR (AUC: 0.83 vs. 0.72 vs. 0.80, P = NS). In addition, QFR-PPG and QFR in combination showed incremental value compared with QFR for predicting RFR (AUC = 0.83 vs. 0.73, P = 0.046, net reclassification index = 0.508, P = 0.001).

CONCLUSION

QFR-PPG significantly correlated with longitudinal MBF gradient and △longitudinal MBF gradient when used for physiological coronary diffuseness assessment. All three parameters had high accuracy in predicting RFR or QFR. Adding physiological diffuseness assessment increased accuracy for predicting myocardial ischemia.

Posttraumatic Stress Disorder, Myocardial Perfusion, and Myocardial Blood Flow: A Longitudinal Twin Study

BACKGROUND

The link between posttraumatic stress disorder (PTSD) and ischemic heart disease remains elusive owing to a shortage of longitudinal studies with a clinical diagnosis of PTSD and objective measures of cardiac compromise.

METHODS

We performed positron emission tomography in 275 twins who participated in two examinations approximately 12 years apart. At both visits, we obtained a clinical diagnosis of PTSD, which was classified as long-standing (both visit 1 and visit 2), late onset (only visit 2), and no PTSD (no PTSD at both visits). With positron emission tomography, we assessed myocardial flow reserve (MFR), which, in absence of significant coronary stenoses, indexes coronary microvascular function. We compared positron emission tomography data at visit 2 across the three categories of longitudinally assessed PTSD and examined changes between the two visits.

RESULTS

Overall, 80% of the twins had no or minimal obstructive coronary disease. Yet, MFR was depressed in twins with PTSD and was progressively lower across groups with no PTSD (2.13), late-onset PTSD (1.97), and long-standing PTSD (1.93) (p = .01). A low MFR (a ratio <2.0) was present in 40% of the twins without PTSD, in 56% of those with late-onset PTSD, and in 72% of those with long-standing PTSD (p < .001). Associations persisted in multivariable analysis, when examining changes in MFR between visit 1 and visit 2, and within twin pairs. Results were similar by zygosity.

CONCLUSIONS

Longitudinally, PTSD is associated with reduced coronary microcirculatory function and greater deterioration over time. The association is especially noted among twins with chronic, long-standing PTSD and is not confounded by shared environmental or genetic factors.

Relation of Obstructive Sleep Apnea in Patients With a Coronary Chronic Total Occlusion to Coronary Collaterals and Mortality

A chronic total occlusion (CTO) is frequently identified in patients undergoing coronary angiography. The prognostic implications of intermittent hypoxia from obstructive sleep apnea (OSA) on patients with a CTO, and effects on collateral recruitment are unknown. The aim of this study was to determine the prevalence, vascular effects, and prognostic implications of the presence of OSA in patients with a CTO. Patients with a CTO between July 2010 and December 2019 were reviewed. Electronic medical records were accessed to determine documented patient history of OSA, demographics, and clinical course. Patients with robust collateral recruitment were defined as Rentrop grade 2 or 3. A total of 948 patients were included in the study, of which 127 (13.4%) had a documented history of OSA. These patients were younger (67.0 years vs 70.6 years, p < 0.01), had a higher body mass index (29.6 kg/m² vs 26.7 kg/m², p < 0.0001), higher rates of hypertension (91.3% vs 83.2%, p < 0.05), higher rates of smokers (63.3% vs 49.0%, p < 0.01) and more use of β-blockers (79% vs 68.5%, p < 0.05) and statins (92.7% vs 82.1%, p < 0.01). A documented history of OSA was independently associated with robust collaterals (OR 3.0 95%CI 1.5 to 5.8, p < 0.01) and lower mortality (HR 0.3 95% CI 0.1 to 0.7, p < 0.01) with a mean survival of 10.8 years, as compared to 8.1 years (log rank p < 0.0001). In conclusion, in patients with a CTO, documented OSA is independently associated with more robust coronary collaterals and lower mortality. The possible cardioprotective implications of intermittent hypoxia in OSA, as well as treatment effect requires further investigation.

"Apical thinning": Relations between myocardial wall thickness and apical left ventricular tracer uptake as assessed with positron emission tomography myocardial perfusion imaging

BACKGROUND

A reduction in left ventricular apical tracer uptake (apical thinning) is frequently observed in myocardial perfusion imaging (MPI), yet its cause remains a matter of debate, particularly in perfusion emission tomography (PET). This analysis sought to determine whether apical thinning in PET-MPI is attributable to true anatomical thinning of the left ventricular apical myocardium.

METHODS AND RESULTS

We retrospectively analyzed 57 patients without any history or signs of apical myocardial infarction who underwent rest PET-MPI with 13N-ammonia and contrast-enhanced cardiac computed tomography (CT). Semi-quantitative normalized percent apical 13N-ammonia uptake at rest, myocardial blood flow (MBF), and k2 wash-out rate constants were compared to apical myocardial wall thickness measurements derived from CT and base-to-apex gradients were calculated. Apical thinning was found in 93% of patients and in 74% when analysis of normalized apical tracer uptake was confined to end-systole. No significant correlation was found between apical myocardial thickness and apical tracer uptake (r = - 0.080, P = .553), MBF (r = - 0.211, P = .115), or k2 wash-out rate (r = - 0.023, P = .872), nor between apical myocardial thickness and any gradients. A statistically significant but small difference in apical myocardial thickness was observed in patients with moderately to severely reduced apical tracer uptake vs patients with normal to mildly reduced uptake (4.3 ± 0.7 mm vs 4.7 ± 0.7 mm; P = .043).

CONCLUSIONS

Apical thinning is a highly prevalent finding during 13N-ammonia PET-MPI that is not solely attributable to true anatomical apical wall thickness or the partial volume effect. Other factors that yet need to be identified seem to have a more prominent impact.

Relationships between myocardial perfusion abnormalities and integrated indices of atherosclerotic burden: clinical impact of combined anatomic-functional evaluation

Aim to evaluate the relationships between functional and anatomical information obtained by myocardial perfusion imaging (MPI) and coronary computed tomography angiography (CCTA) in a series of consecutive patients at intermediate probability of coronary artery disease (CAD). Material and Methods — The study group comprised 139 patients (83 men, age of 61.6±7.5 years) who underwent CCTA and single-photon emission computed tomography myocardial perfusion imaging (SPECT-MPI). Based on CCTA results patients were divided into three groups: 1) with the absence of coronary atherosclerosis on CCTA; 2) with non-obstructive CAD (<50%); 3) with obstructive (≥50%) CAD. The Segment Involvement Score, Segment Stenosis Score (SSS) and CTA Risk Score were calculated as measures of global atherosclerosis burden. MPI studies were considered abnormal in the presence of SSS≥4. Results — Abnormal myocardial perfusion was detected in 60% of cases in group 1 and 2; in 75% of cases in group 3. The overall frequencies of normal and abnormal MPI studies differed significantly only in obstructive CAD patients and did not differ in group 1 and 2. There were no significant correlations between calcium score, atherosclerotic lesion length, positive remodelling index and MPI results in patients with non-obstructive as well as in patients with obstructive CAD. In group of patients with obstructive CAD Segment Stenosis Score correlated wekly with SSS (r=0.39, p=0.001) and SDS (r=0.28; p=0.012); the CTA Risk Score showed correlationes with SSS (r=0.38, p=0.002) and SDS (r=0.30, p=0.020). Conclusion — Myocardial perfusion abnormalities may develop even in the absence of critical coronary artery lesions. The extent of myocardial ischemia correlates with measures of global CAD burden only in patients with obstructive CAD.

Effects of myocardial function and systemic circulation on regional coronary perfusion

Cardiac-coronary interaction and the effects of its pathophysiological variations on spatial heterogeneity of coronary perfusion and myocardial work are still poorly understood. This hypothesis-generating study predicts spatial heterogeneities in both regional cardiac work and perfusion that offer a new paradigm on the vulnerability of the subendocardium to ischemia, particularly at the apex. We propose a mathematical and computational modeling framework to simulate the interaction of left ventricular mechanics, systemic circulation, and coronary microcirculation. The computational simulations revealed that the relaxation rate of the myocardium has a significant effect whereas the contractility has a marginal effect on both the magnitude and transmural distribution of coronary perfusion. The ratio of subendocardial to subepicardial perfusion density (Q_endo/Q_epi) changed by -12 to +6% from a baseline value of 1.16 when myocardial contractility was varied by +25 and -10%, respectively; Q_endo/Q_epi changed by 37% when sarcomere relaxation rate, b, was faster and increased by 10% from the baseline value. The model predicts axial differences in regional myocardial work and perfusion density across the wall thickness. Regional myofiber work done at the apex is 30-50% lower than at the center region, whereas perfusion density in the apex is lower by only 18% compared with the center. There are large axial differences in coronary flow and myocardial work at the subendocardial locations, with the highest differences located at the apex region. A mismatch exists between perfusion density and regional work done at the subendocardium. This mismatch is speculated to be compensated by coronary autoregulation.NEW & NOTEWORTHY We present a model of left ventricle perfusion based on an anatomically realistic coronary tree structure that includes its interaction with the systemic circulation. Left ventricular relaxation rate has a significant effect on the regional distribution of coronary flow and myocardial work.

PET-measured longitudinal flow gradient correlates with invasive fractional flow reserve in CAD patients

Aims

We aimed to evaluate whether a PET-determined longitudinal decrease in myocardial blood flow (MBF) or gradient, assumed as a more specific flow parameter for epicardial resistance, correlates with invasively measured fractional flow reserve (FFR) in coronary artery disease (CAD) patients.

Methods and Results

In 29 patients with suspected or known CAD, myocardial perfusion and MBF in mL/g/min was determined with 13N-ammonia PET/CT during regadenoson stimulation and at rest, and corresponding myocardial flow reserve (MFR = MBF stress/MBF rest) was calculated. MBF parameters were assessed in the myocardial region with stress-related perfusion defect and with stenosis ≥50% (Region 1), without defect but with stenosis ≥50% (Region 2), or without stenosis ≥50% (Region 3). Hyperaemic MBFs were significantly lower in the mid-distal than in the mid-left ventricular myocardium in Regions 1-3 [median and IQ range: 1.57 (1.24, 1.84) vs. 1.87 (1.61, 2.00), and 1.23 (1.11, 1.86) vs. 1.89 (1.80, 1.97), and 1.78 (1.48, 2.00) vs. 1.94 (1.84, 2.05) mL/g/min, P < 0.0001]. Resulting longitudinal MBF gradient during hyperaemic flows was more pronounced in Region 2 than in Regions 1 and 3, respectively [-0.46 (-0.70, -0.10) vs. -0.17 (-0.29, -0.11) and -0.15 (-0.25, -0.09) mL/g/min, respectively, P < 0.01]. There was a significant correlation between the hyperaemic longitudinal MBF gradient and FFR (r = 0.95; P < 0.0001), while this association was less pronounced for corresponding MFR (r = 0.50; P = 0.006).

Conclusion

The observed close correlation between a longitudinal MBF gradient during hyperaemic flows and invasively measured FFR suggests the longitudinal flow gradient as an emerging non-invasive index of flow-limiting CAD.

Diffuse coronary artery disease among other atherosclerotic plaque characteristics by coronary computed tomography angiography for predicting coronary vessel-specific ischemia by fractional flow reserve

BACKGROUND AND AIMS

Coronary computed tomography angiography (CCTA) permits effective identification of diffuse CAD and atherosclerotic plaque characteristics (APCs). We sought to examine the usefulness of diffuse CAD beyond luminal narrowing and APCs by CCTA to detect vessel-specific ischemia.

METHODS

407 vessels (n = 252 patients) from the DeFACTO diagnostic accuracy study were retrospectively analyzed for percent plaque diffuseness (PD). Percent plaque diffuseness (PD) was obtained on per-vessel level by summation of all contiguous lesion lengths and divided by total vessel length, and was logarithmically transformed (log percent PD). Additional CCTA measures of stenosis severity including minimal lumen diameter (MLD), and APCs, such as positive remodeling (PR) and low attenuation plaque (LAP), were also included. Vessel-specific ischemia was defined as fractional flow reserve (FFR) ≤0.80. Multivariable regression, discrimination by area under the receiver operating characteristic curve (AUC), and category-free net reclassification improvement (cNRI) were assessed.

RESULTS

Backward stepwise logistic regression revealed that for every unit increase in log percent PD, there was a 58% (95% CI: 1.01-2.48, p = 0.048) rise in the odds of having an abnormal FFR, independent of stenosis severity and APCs. The AUC indicated no further improvement in discriminatory ability after adding log percent PD to the final parsimonious model of MLD, PR, and LAP (AUC difference: 0.003, 95% CI: -0.003-0.010, p = 0.33). Conversely, adding log percent PD to the base model of MLD, PR, and LAP improved cNRI by 0.21 (95% CI: 0.01-0.41, p < 0.001).

CONCLUSIONS

Accounting for diffuse CAD may help improve the accuracy of CCTA for detecting vessel-specific ischemia.

Longitudinal myocardial blood flow gradient and CAD detection

Conventional myocardial perfusion scintigraphy with SPECT/CT or with PET/CT has been established as pivotal clinical imaging modality for the identification of hemodynamically obstructive coronary artery disease (CAD) and risk stratification of patients with suspected or known CAD. While the assessment of the relative distribution of radiotracer uptake in the left-ventricular (LV) myocardium during vasomotor stress identifies the "culprit" or most severe CAD lesion in multivessel disease, flow-limiting effects of remaining but less severe epicardial lesions may be missed. This limitation principally may be overcome by the possibility of PET/CT with radiotracer-kinetic modeling to concurrently assess left-ventricular (LV) myocardial blood flow (MBF) in ml/g/min at rest and during vasomotor stress and the resulting myocardial flow reserve (MFR). While a stress-induced regional reduction in radiotracer uptake or perfusion identifies the most advanced epicardial lesion, flow-limiting effects of the other epicardial lesions may principally be identified by regional reductions in MFR. Conversely, reductions in MFR in CAD may be appreciated as suboptimal as they reflect not only the consequences of flow-limiting effects of epicardial stenosis but also of microvascular dysfunction. The relatively low specificity of a reduced therefore MFR may hamper a clear identification of the downstream hemodynamic effects of an epicardial lesion on hyperemic coronary flow increases. In this scenario, there is increasing evidence that the PET assessment of an abnormal decrease in MBF from the base to the apex of the LV during hyperemic flows, a so-called longitudinal flow gradient, is primarily related to fluid dynamic consequences of CAD-induced diffuse luminal and/or focal narrowing of the epicardial artery. The combined evaluation of the MFR and corresponding longitudinal MBF gradient could emerge as new a novel analytic concept to further optimize the identification and characterization of hemodynamic CAD burden in multivessel disease, which, however, warrants further clinical validation.

Quantitative relationship between coronary artery calcium score and hyperemic myocardial blood flow as assessed by hybrid 15O-water PET/CT imaging in patients evaluated for coronary artery disease

BACKGROUND

The incremental value of CAC over traditional risk factors to predict coronary vasodilator dysfunction and inherent myocardial blood flow (MBF) impairment is only scarcely documented (MBF). The aim of this study was therefore to evaluate the relationship between CAC content, hyperemic MBF, and coronary flow reserve (CFR) in patients undergoing hybrid (15)O-water PET/CT imaging.

METHODS

We evaluated 173 (mean age 56 ± 10, 78 men) patients with a low to intermediate likelihood for coronary artery disease (CAD), without a documented history of CAD, undergoing vasodilator stress (15)O-water PET/CT and CAC scoring. Obstructive coronary artery disease was excluded by means of invasive (n = 44) or CT-based coronary angiography (n = 129).

RESULTS

91 of 173 patients (52%) had a CAC score of zero. Of those with CAC, the CAC score was 0.1-99.9, 100-399.9, and ≥400 in 31%, 12%, and 5% of patients, respectively. Global CAC score showed significant inverse correlation with hyperemic MBF (r = -0.32, P < .001). With increasing CAC score, there was a decline in hyperemic MBF on a per-patient basis [3.70, 3.30, 2.68, and 2.53 mL · min(-1) · g(-1), with total CAC score of 0, 0.1-99.9, 100-399.9, and ≥400, respectively (P < .001)]. CFR showed a stepwise decline with increasing levels of CAC (3.70, 3.32, 2.94, and 2.93, P < .05). Multivariate analysis, including age, BMI, and CAD risk factors, revealed that only age, male gender, BMI, and hypercholesterolemia were associated with reduced stress perfusion. Furthermore, only diabetes and age were independently associated with CFR.

CONCLUSION

In patients without significant obstructive CAD, a greater CAC burden is associated with a decreased hyperemic MBF and CFR. However, this association disappeared after adjustment for traditional CAD risk factors. These results suggest that CAC does not add incremental value regarding hyperemic MBF and CFR over established CAD risk factors in patients without obstructive CAD.

Cardiac abnormalities in severe acute dichlorvos poisoning

OBJECTIVE

Patients with organophosphorus poisoning sometimes die suddenly during rigorous treatment, possibly from myocardial injury. This study sought to elucidate the mechanisms underlying organophosphorus poisoning-induced cardiotoxicity.

DESIGN

Prospective observational study.

SETTING

Urban, tertiary teaching hospital emergency intensive care unit with 10 beds.

PATIENTS

Forty-one patients with severe acute dichlorvos poisoning were consecutively enrolled (n = 92) at emergency intensive care unit and followed for 3 months.

MEASUREMENTS AND MAIN RESULTS

Levels of serum creatine kinase isoenzyme myocardium, cardiac troponin I, acetylcholinesterase, acetylcholine, epinephrine, and norepinephrine were tested on hospital days 1, 3, and 5 and on discharge day. Electrocardiography was recorded on admission and then every other day. Transthoracic echocardiography was performed at admission, in the acute phase, before discharge, and during follow-up. Technetium 99m-sestamibi myocardial single photon emission computed tomography was conducted in four patients. Thirty-seven (90.2%) patients survived and four (9.8%) patients died during treatment. We observed sinus tachycardia in 37 (90.2%) patients and ST-T changes in 33 (80.4%) patients. Creatine kinase isoenzyme myocardium and cardiac troponin I levels peaked at day 3 postadmission and then decreased to normal levels. Serum acetylcholine, epinephrine, and norepinephrine peaked at day 1 after admission and then decreased. Echocardiography revealed marked decreases in wall motion of the interventricular septum and left ventricle in the acute phase but returned to normal in the recovery phase. The left ventricular ejection fraction improved significantly from 42 ± 5% to 59 ± 4% (p = .001). Single photon emission computed tomography showed abnormal left ventricle perfusion.

CONCLUSION

Severe acute dichlorvos poisoning is associated with reversible myocardial dysfunction, possibly through an increase in catecholamine levels.

Left ventricular contraction patterns in patients with suspected acute coronary syndrome and normal coronary angiograms: a new look at the takotsubo syndrome

BACKGROUND

Original descriptions of the takotsubo syndrome (TS) included a characteristic left ventricular (LV) contraction pattern, "apical ballooning." Recently, several reports have associated contraction patterns not strictly conforming to the original description with TS. The specifics of the contraction pattern seem to set TS apart from the much larger population of patients with acute coronary syndrome (ACS) but no obstructive coronary artery disease (OCAD). This study was undertaken to compare patients with midventricular and apical dysfunction with those with other LV contraction patterns.

HYPOTHESIS

If TS can present with a variety of patterns of LV dysfunction, then both those with and those without the pattern should have the clinical components previously assigned to the syndrome.

METHODS

We studied LV contraction patterns in consecutive ACS patients referred for consideration of emergent or urgent percutaneous coronary intervention.

RESULTS

Of the 893 patients evaluated in 2008, we excluded 862 on the basis of OCAD, preexisting LV dysfunction, or an obvious alternative cause of symptoms. The remaining 31 (3.5%) also had no OCAD but manifested an LV contraction abnormality. We compared the 15 patients (1.7%) whose ventriculograms met criteria for TS with the 16 patients (1.8%) whose did not. The most common alternative pattern was global hypokinesis, followed by a variety of segmental contraction abnormalities. Patients with the TS pattern were older and had evidence of greater myocardial injury. More than 85% were women.

CONCLUSIONS

The TS pattern identifies a distinct subset of ACS patients with a remarkable predominance of postmenopausal women and is therefore fundamental to the definition of this entity. This distinctive facet of the syndrome is likely to be an important clue to its pathogenesis. We did not encounter patients with other patterns of LV dysfunction that could be thought to represent stress-induced cardiomyopathy. Copyright © 2011 Wiley Periodicals, Inc. The authors have no funding, financial relationships, or conflicts of interest to disclose.

Structural epicardial disease and microvascular function are determinants of an abnormal longitudinal myocardial blood flow difference in cardiovascular risk individuals as determined with PET/CT

BACKGROUND

The aim of this study was to determine whether epicardial structural disease may affect the manifestation of a longitudinal decrease in myocardial blood flow (MBF) or MBF difference during hyperemia in cardiovascular risk individuals, and its dependency on the flow increase.

METHODS AND RESULTS

In 54 cardiovascular risk individuals (at risk) and in 26 healthy controls, MBF was measured with (13)N-ammonia and PET/CT in mL/g/min at rest and during dipyridamole stimulation. Computed tomography coronary angiography (CTA) was performed using a 64-slice CT of a PET/CT system. Absolute MBFs during dipyridamole stimulation were mildly lower in the mid-distal than in the mid-LV myocardium in controls (2.20 ± .51 vs 2.29 ± .51, P < .0001), while it was more pronounced in at risk with normal and abnormal CTA (1.56 ± .42 vs 1.91 ± .46 and 1.18 ± .34 vs 1.51 ± .40 mL/g/min, respectively, P < .0001), resulting in a longitudinal MBF difference that was highest in at risk with normal CTA, intermediate in at risk abnormal CTA, and lowest in controls (.35 ± .16 and .22 ± .09 vs .09 ± .04 mL/g/min, respectively, P < .0001). On multivariate analysis, log-CCS and mid-LV hyperemic MBF increase, indicative of microvascular function, were independent predictors of the observed longitudinal MBF difference (P ≤ .004 by ANOVA).

CONCLUSIONS

Epicardial structural disease and microvascular function are important determinants of an abnormal longitudinal MBF difference as determined with PET/CT.

Pathogenesis of the Takotsubo syndrome: a unifying hypothesis

The takotsubo syndrome (TS) is defined by a constellation of clinical observations in a subgroup of patients with acute coronary syndromes. Separating patients with TS from the general population with acute ischemic events are 2 important findings: obstructive coronary artery disease is missing, but the sine qua non is a distinctive pattern of abnormal left ventricular contraction. As with many newly recognized clinical syndromes, TS seems not to conform to accepted pathogenetic mechanisms. Thus, physicians are challenged to identify previously unrecognized mechanisms of disease. Two schools of thought have emerged in this regard. Most consider its pathogenesis to be a stress-induced neurohormonal phenomenon, while a smaller but substantial group believe that the transient occlusion of an epicardial coronary artery is responsible and that the syndrome is simply an unusual manifestation of coronary atherosclerosis. This editorial outlines briefly the evidence for each of these positions and presents a novel construct that may encompass the 2 views. Central to this unifying hypothesis is the belief that a neurohormonal surge triggers the hallmark left ventricular contraction abnormality, the sine qua non of the TS. In conclusion, the authors postulate that this pattern will result regardless of the state of the epicardial coronary arteries and can be observed in patients with angiographically normal coronary arteries, as well as those with obstructed or occluded arteries.

Preoperative Takotsubo cardiomyopathy identified in the operating room before induction of anesthesia

We present a case of Takotsubo cardiomyopathy recognized in a patient just before induction of anesthesia. The patient's anxiety about surgery could have been an inciting factor. As the patient's surgery was cancelled and rescheduled for a later date, treatment and strategies to prevent recurrence of the syndrome are discussed.

Quantification of myocardial blood flow: what is the clinical role?

Quantification of regional myocardial blood flow and of its responses to targeted physiologic and pharmacologic interventions, which is now available with positron emitting tracers of blood flow and positron emission tomography (PET), extends the diagnostic potential of standard myocardial perfusion imaging. These noninvasive flow measurements serve as tools for quantifying functional consequences of epicardial coronary artery disease, as well as of impairments in microcirculatory reactivity that escape detection by standard perfusion imaging. Flow measurements are clinically useful for more comprehensively assessing the extent and severity of coronary vascular disease or impairments in microcirculatory function in noncoronary cardiac disease. Flow estimates in these disorders contain independent or unique prognostic information about future major cardiac events. Flow measurements are also useful for assessing the coronary risk, for predicting long-term cardiovascular events, and for monitoring the effectiveness of risk reduction strategies.

Unusual case of left ventricular ballooning involving the inferior wall: a case report

Background

Tako – tsubo like syndrome (also named left ventricular apical ballooning) is an unusual cardiomyopathy with an high incidence in Japanese population of female sex, following an emotional stress. The clinical features (typical chest pain), and the electrocardiographic changes (negative T wave and persistent ST elevation in anterior leads), are suggestive of an acute myocardial infarction; nevertheless the coronary angiography show coronary arteries without lesions and the ventriculography show specific segmental dysfunction. In the literature there are many reports of typical left ventricular ballooning (apical); due to the rarity of the atypical localizations (such as mid, basal, anterior or inferior left ventricular wall) many authors think they are different physiopatologic entity.

Case report

We report a case of 50 – years old woman, with a family history of ischeamic cardiomyopathy but with no additional cardiovascular risk factors, who arrived to emergency department with a recent episode of chest pain (about 30 minutes) with electrocardiographic and echocardiographic features suggested of a inferior ST elevation myocardial infarction. Coronary angiography showed coronary arteries without atherosclerotic lesions; ventriculography showed an inferior dysfunction.

Conclusion

This data can suggest for an atypical form (in term of clinical presentation and localization) of left ventricular ballooning involving the inferior wall (never described in the literature), not preceded by any emotional or physical stress. The follow – up performed by transthoracic echocardiography (2 months later) revealed a complete regression of wall motions abnormalities.

Structural alterations of the coronary arterial wall are associated with myocardial flow heterogeneity in type 2 diabetes mellitus

PURPOSE

To determine the relationship between carotid intima-media thickness (IMT), coronary artery calcification (CAC), and myocardial blood flow (MBF) at rest and during vasomotor stress in type 2 diabetes mellitus (DM).

METHODS

In 68 individuals, carotid IMT was measured using high-resolution vascular ultrasound, while the presence of CAC was determined with electron beam tomography (EBT). Global and regional MBF was determined in milliliters per gram per minute with (13)N-ammonia and positron emission tomography (PET) at rest, during cold pressor testing (CPT), and during adenosine (ADO) stimulation.

RESULTS

There was neither a relationship between carotid IMT and CAC (r = 0.10, p = 0.32) nor between carotid IMT and coronary circulatory function in response to CPT and during ADO (r = -0.18, p = 0.25 and r = 0.10, p = 0.54, respectively). In 33 individuals, EBT detected CAC with a mean Agatston-derived calcium score of 44 +/- 18. There was a significant difference in regional MBFs between territories with and without CAC at rest and during ADO-stimulated hyperemia (0.69 +/- 0.24 vs. 0.74 +/- 0.23 and 1.82 +/- 0.50 vs. 1.95 +/- 0.51 ml/g/min; p < or = 0.05, respectively) and also during CPT in DM but less pronounced (0.81 +/- 0.24 vs. 0.83 +/- 0.23 ml/g/min; p = ns). The increase in CAC was paralleled with a progressive regional decrease in resting as well as in CPT- and ADO-related MBFs (r = -0.36, p < or = 0.014; r = -0.46, p < or = 0.007; and r = -0.33, p < or = 0.041, respectively).

CONCLUSIONS

The absence of any correlation between carotid IMT and coronary circulatory function in type 2 DM suggests different features and stages of early atherosclerosis in the peripheral and coronary circulation. PET-measured MBF heterogeneity at rest and during vasomotor stress may reflect downstream fluid dynamic effects of coronary artery disease (CAD)-related early structural alterations of the arterial wall.

Reversible impairment of coronary flow reserve in takotsubo cardiomyopathy: a myocardial PET study

BACKGROUND

The precise etiology of takotsubo cardiomyopathy remains unclear. The study of myocardial blood flow (MBF) and coronary flow reserve (CFR) by use of positron emission tomography might help in understanding this syndrome.

METHODS AND RESULTS

Three postmenopausal women underwent adenosine/rest perfusion with nitrogen 13 ammonia and metabolism with fluorine 18 fluorodeoxyglucose positron emission tomography, coronary angiography, cardiac magnetic resonance, and echocardiography in the acute phase of takotsubo cardiomyopathy and at 3 months' follow-up, after normalization of left ventricular function. PET study was performed in 2 parts: the perfusion analysis with nitrogen ammonia and the metabolism of the heart using FDG. MBF and CFR were analyzed quantitatively in the acute phase and at follow-up. The images highlighted the impairment of tissue metabolism in the dysfunctioning left ventricular segments in the acute phase, mainly in the apical segments and progressively less in the medium segments. At the same time, a clear inverse metabolic/perfusion mismatch emerged, which normalized 3 months later. The quantitative analysis of MBF showed a reduction in the acute phase in apical segments in comparison to basal segments without differences between midventricular and basal segments. In the acute phase CFR proved to be reduced in apical versus basal segments. CFR impairment of apical segments recovered completely after 3 months.

CONCLUSION

The acute phase of takotsubo cardiomyopathy is characterized by an inverse perfusion/metabolism mismatch with a reduction in CFR in the apical segments. However, the impairment of CFR and the reduction of metabolism in the apical segments recovered completely after 3 months.

Reversible impairment of coronary flow reserve in takotsubo cardiomyopathy: a myocardial PET study

BACKGROUND

The precise etiology of takotsubo cardiomyopathy remains unclear. The study of myocardial blood flow (MBF) and coronary flow reserve (CFR) by use of positron emission tomography might help in understanding this syndrome.

METHODS AND RESULTS

Three postmenopausal women underwent adenosine/rest perfusion with nitrogen 13 ammonia and metabolism with fluorine 18 fluorodeoxyglucose positron emission tomography, coronary angiography, cardiac magnetic resonance, and echocardiography in the acute phase of takotsubo cardiomyopathy and at 3 months' follow-up, after normalization of left ventricular function. PET study was performed in 2 parts: the perfusion analysis with nitrogen ammonia and the metabolism of the heart using FDG. MBF and CFR were analyzed quantitatively in the acute phase and at follow-up. The images highlighted the impairment of tissue metabolism in the dysfunctioning left ventricular segments in the acute phase, mainly in the apical segments and progressively less in the medium segments. At the same time, a clear inverse metabolic/perfusion mismatch emerged, which normalized 3 months later. The quantitative analysis of MBF showed a reduction in the acute phase in apical segments in comparison to basal segments without differences between midventricular and basal segments. In the acute phase CFR proved to be reduced in apical versus basal segments. CFR impairment of apical segments recovered completely after 3 months.

CONCLUSION

The acute phase of takotsubo cardiomyopathy is characterized by an inverse perfusion/metabolism mismatch with a reduction in CFR in the apical segments. However, the impairment of CFR and the reduction of metabolism in the apical segments recovered completely after 3 months.

Local release of catecholamines from the hearts of patients with tako-tsubo-like left ventricular dysfunction

BACKGROUND

The precise mechanism of tako-tsubo-like left ventricular (LV) dysfunction remains unclear, although recent studies have shown that activation of sympathetic tone might be involved. However, local release of catecholamines from cardiac sympathetic efferent neurons in patients with tako-tsubo-like LV dysfunction remains poorly understood. The purpose of this study was to investigate evidence of local release of catecholamines from the hearts of patients with tako-tsubo-like LV dysfunction.

METHODS AND RESULTS

Five consecutive patients with tako-tsubo-like LV dysfunction were studied. After confirming LV apical ballooning and a normal coronary angiogram, sampling of blood for the measurement of plasma catecholamine levels was performed at the aortic root (Ao) and coronary sinus (CS). In all 5 cases, increased local release of norepinephrine from the heart was documented (597, 4,238, 2,121, 486, 371 pg/ml at the Ao; 836, 5,719, 3,386, 658, 472 pg/ml at the CS, respectively).

CONCLUSIONS

Increased cardiac catecholamines might cause the transient LV apical ballooning in patients with tako-tsubo-like LV dysfunction.

The clinical features of transient left ventricular nonapical ballooning syndrome: comparison with apical ballooning syndrome

BACKGROUND

Recently, several cases of atypical left ventricular (LV) ballooning syndrome without involvement of the LV apex have been reported. However, there has been no assessment of the clinical features of this novel presentation or comparison with the typical transient LV apical ballooning syndrome.

METHODS

We evaluated 47 patients diagnosed with transient LV ballooning syndrome. The diagnostic criteria were (1) transient akinesia/dyskinesia beyond a single major coronary artery vascular distribution, (2) absence of significant coronary artery disease on coronary angiograms, and (3) new electrocardiographic changes.

RESULTS

Thirty-one patients showed classic LV apical ballooning, and 16 showed atypical LV ballooning without involvement of the LV apex (nonapical ballooning). Clinical presentations and inhospital courses of illness were mostly similar among patients with nonapical ballooning (group NA) and patients with apical ballooning (group A). However, on admission, there were fewer patients with cardiogenic shock or pulmonary edema in group NA than in group A (19% vs 48%, P = .048). Group NA patients were relatively younger than group A patients (median ages 58 vs 70 years, P = .02), and fewer patients had coronary risk factors in group NA than in group A (38% vs 77%, P = .01). On electrocardiogram, T-wave inversion was noted less frequently in the NA group than in the A group (69% vs 97%, P = .01).

CONCLUSIONS

Transient LV nonapical ballooning syndrome and classic LV apical ballooning syndrome may be different manifestations of a single syndrome. They appear to have differences in the severity of heart failure, in patient characteristics, and in electrocardiographic change.

Diagnostic value of PET-measured heterogeneity in myocardial blood flows during cold pressor testing for the identification of coronary vasomotor dysfunction

BACKGROUND

We aimed to evaluate the diagnostic value of a positron emission tomography (PET)-measured heterogeneity in longitudinal myocardial blood flow (MBF) during cold pressor testing (CPT) and global MBF response to CPT from rest (DeltaMBF) for identification of coronary vasomotor dysfunction.

METHODS AND RESULTS

In 35 patients CPT-induced alterations in epicardial luminal area were determined with quantitative angiography as the reference. MBF was assessed over the whole left ventricle as global MBF and regionally in the mid and mid-distal myocardium as MBF difference or MBF heterogeneity with nitrogen-13 ammonia and PET. The sensitivity and specificity of a longitudinal MBF difference during CPT in the identification of epicardial vasomotor dysfunction were significantly higher than the global DeltaMBF to CPT (88% vs 79% and 82% vs 64%, respectively; P < .05). Combining both parameters resulted in an optimal sensitivity of 100% at the expense of an intermediate specificity of 73%. The diagnostic accuracy was higher for the combined analysis than that for the MBF difference alone and global DeltaMBF alone (91% vs 86% and 74%, respectively; P < .05).

CONCLUSIONS

The combined evaluation of a CPT-induced heterogeneity in longitudinal MBF and the change in global MBF from rest may emerge as a new promising analytic approach to further optimize the identification and characterization of coronary vasomotor dysfunction.

Positron emission tomography in coronary artery disease

PURPOSE OF REVIEW

Mortality and coronary events are dramatically reduced in coronary artery disease by intense lifestyle and pharmacologic management without further improvement by revascularization procedures, thereby requiring definitive noninvasive diagnostic imaging. Consequently, this review summarizes the evidence supporting cardiac positron emission tomography as a definitive, noninvasive, 'one-stop' test for routine management of coronary artery disease that is well validated in the scientific literature and illustrated by clinical cases.

RECENT FINDINGS

Substantial evidence documents accuracy of positron emission tomography for identifying early or advanced coronary artery disease, quantifying its severity, risk stratification, deciding on revascularization procedures, following progression or regression and for evaluating coronary endothelial function as the basis for preventive treatment. Recent technology like positron emission tomography-computed tomography, however, requires advanced knowledge, training and attention to technical details to avoid common artifactual results and to provide definitive conclusions illustrated in this review.

SUMMARY

Cardiac positron emission tomography, done correctly with attention to technical details, provides definitive noninvasive assessment of early or advanced coronary atherosclerosis as the basis for invasive procedures or for lifelong intense risk factor management, demonstrates progression or regression of disease, predicts clinical outcomes and serves as the primary definitive noninvasive guide for managing coronary artery disease.

Acute impairment of regional myocardial glucose uptake in the apical ballooning (takotsubo) syndrome

BACKGROUND

Apical ballooning syndrome (ABS) is a poorly understood clinical entity characterized by acute, transient systolic dysfunction of the left ventricular (LV) apex in the absence of epicardial coronary artery disease and commonly associated with acute emotional stress. We report abnormal regional myocardial perfusion and glucose uptake in 4 consecutive ABS patients studied using positron emission tomography with 13N-ammonia and 18F-fluorodeoxyglucose within 72 hours of presentation with ABS.

METHODS

All patients were postmenopausal females, 3 of whom had a major recent life stress event. Coronary angiography revealed no or minimal obstructive epicardial coronary artery disease. All patients exhibited reduced glucose uptake in the mid-LV and apical myocardial segments, which was out of proportion to perfusion abnormalities in half of the cases.

CONCLUSION

In all 4 patients, affected regions subsequently recovered regional LV systolic function within 6 weeks.

Acute impairment of regional myocardial glucose uptake in the apical ballooning (takotsubo) syndrome

BACKGROUND

Apical ballooning syndrome (ABS) is a poorly understood clinical entity characterized by acute, transient systolic dysfunction of the left ventricular (LV) apex in the absence of epicardial coronary artery disease and commonly associated with acute emotional stress. We report abnormal regional myocardial perfusion and glucose uptake in 4 consecutive ABS patients studied using positron emission tomography with 13N-ammonia and 18F-fluorodeoxyglucose within 72 hours of presentation with ABS.

METHODS

All patients were postmenopausal females, 3 of whom had a major recent life stress event. Coronary angiography revealed no or minimal obstructive epicardial coronary artery disease. All patients exhibited reduced glucose uptake in the mid-LV and apical myocardial segments, which was out of proportion to perfusion abnormalities in half of the cases.

CONCLUSION

In all 4 patients, affected regions subsequently recovered regional LV systolic function within 6 weeks.

Apical ballooning syndrome or takotsubo cardiomyopathy: a systematic review

AIMS

To clarify the major features of the apical ballooning syndrome, we performed a systematic review of the existing literature.

METHODS AND RESULTS

Review of all relevant case series using the MEDLINE and EMBASE databases resulted in the identification of 14 studies. These studies suggest that the apical ballooning syndrome accounts for approximately 2.0% of ST-segment elevation infarcts, with most cases described in post-menopausal women. The most common clinical presentations are chest pain and dyspnoea, reported in 67.8 and 17.8% of the patients, respectively. Cardiogenic shock (4.2% of the patients) and ventricular fibrillation (1.5%) were not infrequent. ST-segment elevation was reported in 81.6% of the patients, T wave abnormalities in 64.3%, and Q waves in 31.8%. Cardiac biomarkers were usually mildly elevated, as reported in 86.2% of the patients. Typically, patients had left ventricular (LV) dysfunction on admission, with mean ejection fraction ranging from 20 to 49%. However, over a period of days to weeks, all patients experienced dramatic improvement in LV function. The onset of symptoms was often preceded by emotional (26.8%) or physical stress (37.8%). Norepinephrine concentration was elevated in 74.3% of the patients. Prognosis was generally excellent, with full recovery in most patients. In-hospital mortality was 1.1%. Only 3.5% of the patients experienced a recurrence.

CONCLUSION

Clinicians should consider this syndrome in the differential diagnosis of patients presenting with chest pain, especially in post-menopausal women with a recent history of emotional or physical stress.

PET-measured heterogeneity in longitudinal myocardial blood flow in response to sympathetic and pharmacologic stress as a non-invasive probe of epicardial vasomotor dysfunction

PURPOSE

We investigated whether a myocardial perfusion gradient during pharmacologically induced hyperemia also occurred during sympathetic stimulation with cold pressor testing (CPT), which commonly induces a paradoxical coronary vasoconstriction in individuals with coronary risk factors.

METHODS

Myocardial blood flow (MBF) was measured in absolute units (ml/g/min) with 13N-ammonia and PET at rest, during CPT, and during pharmacologic vasodilation in 59 participants with coronary risk factors ("at risk") and in 43 healthy individuals (controls). MBF was assessed globally as mean MBF, and in the mid and mid-distal myocardium of the left ventricle (LV). A decrease in MBF from mid to mid-distal LV myocardium was defined as MBF difference indicative of a perfusion gradient.

RESULTS

The change in mean MBF to CPT (DeltaMBF) in the at-risk group was significantly reduced compared with controls (0.05+/-0.19 vs 0.31+/-0.20 ml/g/min, p<0.0001), whereas mean MBF during pharmacologic vasodilation in the at-risk group tended to be lower than in controls (1.72+/-0.71 vs 2.00+/-0.64 ml/g/min, p=NS). Absolute MBFs during CPT and pharmacologic vasodilation were significantly lower in the mid-distal than in the mid LV myocardium, resulting in a significant MBF difference in the at-risk group (0.15+/-0.06 and 0.27+/-0.12 ml/g/min, p<0.0001) that was not observed in controls (0.007+/-0.05 and 0.014+/-0.10 ml/g/min, p=NS). In the at-risk group there was a significant correlation between the difference of mid to mid-distal MBF during CPT and that during pharmacologic vasodilation (r=0.43, p<0.004), suggesting functional alterations of epicardial vessels as the predominant cause for the observed MBF difference.

CONCLUSION

The relative decrease in MBF from the mid to the mid-distal left-ventricular myocardium suggests an intracoronary pressure decline during CPT and pharmacologic vasodilation, which is likely to reflect an impairment of flow-mediated epicardial vasomotor function.

Quantitative relation between hemodynamic changes during intravenous adenosine infusion and the magnitude of coronary hyperemia: implications for myocardial perfusion imaging

OBJECTIVES

The goal of this study was to determine the relationship between changes in cardiac hemodynamics during intravenous adenosine (ADO) infusion, and myocardial blood flow (MBF).

BACKGROUND

The relationship between changes in MBF and the peripheral hemodynamic effects during peak adenosine infusion is unknown.

METHODS

We studied 348 (age 57 +/- 11 years; 106 females) without evidence of obstructive coronary artery disease by positron emission tomography (PET). Patients underwent [(13)N]ammonia PET imaging to measure MBF and coronary vascular resistance (CVR) at rest and during a standard 6-min ADO infusion. Changes in heart rate (HR) and mean arterial pressure (MAP) were measured at baseline and during peak hyperemia.

RESULTS

During ADO, HR increased (delta: 24 +/- 11 beats/min) and MAP decreased (delta: -2 +/- 10 mm Hg). Overall, delta HR correlated poorly with hyperemic MBF (R = 0.10, p = 0.06) and with CVR (R = 0.11, p = 0.04). Delta MAP also showed a weak correlation with hyperemic MBF (R = 0.04, p = 0.44) and with CVR (R = 0.11, p = 0.04). Patients in the lowest tertile for delta HR showed a 7% lower hyperemic MBF (1.84 +/- 0.6 ml/min/g vs. 1.98 +/- 0.6 ml/min/g, p = 0.022) and an 8% higher CVR (54 +/- 20 mm Hg/ml/min/g vs. 50 +/- 17 mm Hg/ml/min/g, p = 0.056) compared with those in the highest tertile. Patients in the lowest tertile for delta MAP (i.e., greatest decline) showed similar hyperemic MBF, and an 8% lower CVR compared with those in the highest tertile (p = NS for both). These small differences between tertiles remain, even after adjusting for differences in age, gender, smoking status, and lipid profile.

CONCLUSIONS

Changes in cardiac hemodynamics during intravenous ADO are generally poor predictors of changes in MBF and CVR during peak hyperemia, and, thus, they should not be used to assess the effectiveness of vasodilator stress in myocardial perfusion imaging.

Neurohumoral features of myocardial stunning due to sudden emotional stress

BACKGROUND

Reversible left ventricular dysfunction precipitated by emotional stress has been reported, but the mechanism remains unknown.

METHODS

We evaluated 19 patients who presented with left ventricular dysfunction after sudden emotional stress. All patients underwent coronary angiography and serial echocardiography; five underwent endomyocardial biopsy. Plasma catecholamine levels in 13 patients with stress-related myocardial dysfunction were compared with those in 7 patients with Killip class III myocardial infarction.

RESULTS

The median age of patients with stress-induced cardiomyopathy was 63 years, and 95 percent were women. Clinical presentations included chest pain, pulmonary edema, and cardiogenic shock. Diffuse T-wave inversion and a prolonged QT interval occurred in most patients. Seventeen patients had mildly elevated serum troponin I levels, but only 1 of 19 had angiographic evidence of clinically significant coronary disease. Severe left ventricular dysfunction was present on admission (median ejection fraction, 0.20; interquartile range, 0.15 to 0.30) and rapidly resolved in all patients (ejection fraction at two to four weeks, 0.60; interquartile range, 0.55 to 0.65; P<0.001). Endomyocardial biopsy showed mononuclear infiltrates and contraction-band necrosis. Plasma catecholamine levels at presentation were markedly higher among patients with stress-induced cardiomyopathy than among those with Killip class III myocardial infarction (median epinephrine level, 1264 pg per milliliter [interquartile range, 916 to 1374] vs. 376 pg per milliliter [interquartile range, 275 to 476]; norepinephrine level, 2284 pg per milliliter [interquartile range, 1709 to 2910] vs. 1100 pg per milliliter [interquartile range, 914 to 1320]; and dopamine level, 111 pg per milliliter [interquartile range, 106 to 146] vs. 61 pg per milliliter [interquartile range, 46 to 77]; P<0.005 for all comparisons).

CONCLUSIONS

Emotional stress can precipitate severe, reversible left ventricular dysfunction in patients without coronary disease. Exaggerated sympathetic stimulation is probably central to the cause of this syndrome.

Cardiac positron emission tomography imaging

Cardiac positron emission tomography (PET) imaging has advanced from primarily a research tool to a practical, high-performance clinical imaging modality. The widespread availability of state-of-the-art PET gamma cameras, the commercial availability of perfusion and viability PET imaging tracers, reimbursement for PET perfusion and viability procedures by government and private health insurance plans, and the availability of computer software for image display of perfusion, wall motion, and viability images have all been a key to cardiac PET imaging becoming a routine clinical tool. Although myocardial perfusion PET imaging is an option for all patients requiring stress perfusion imaging, there are identifiable patient groups difficult to image with conventional single-photon emission computed tomography imaging that are particularly likely to benefit from PET imaging, such as obese patients, women, patients with previous nondiagnostic tests, and patients with poor left ventricular function attributable to coronary artery disease considered for revascularization. Myocardial PET perfusion imaging with rubidium-82 is noteworthy for high efficiency, rapid throughput, and in a high-volume setting, low operational costs. PET metabolic viability imaging continues to be a noninvasive standard for diagnosis of viability imaging. Cardiac PET imaging has been shown to be cost-effective. The potential of routine quantification of resting and stress blood flow and coronary flow reserve in response to pharmacologic and cold-pressor stress offers tantalizing possibilities of enhancing the power of PET myocardial perfusion imaging. This can be achieved by providing assurance of stress quality control, in enhancing diagnosis and risk stratification in patients with coronary artery disease, and expanding diagnostic imaging into the realm of detection of early coronary artery disease and endothelial dysfunction subject to risk factor modification. Combined PET and x-ray computed tomography imaging (PET-CT) results in enhanced patient throughput and efficiency. The combination of multislice computed tomography scanners with PET opens possibilities of adding coronary calcium scoring and noninvasive coronary angiography to myocardial perfusion imaging and quantification. Evaluation of the clinical role of these creative new possibilities warrants investigation.