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.

Choosing between anatomy and function is not always evident for the heart of end-stage renal disease patients. How low can we go?

Patients with chronic kidney disease (CKD) are at a very high risk of adverse cardiovascular events. In CKD patients, vascular calcification is more prevalent, appears at an earlier age, and is more severe than in the general population. CKD physiology rather than the effects of dialysis is the primary driver of microvascular disease in these patients. Considering the significant morbidity and mortality attributable to cardiovascular disease in the CKD population, risk stratification remains an important challenge. Topics such as function vs anatomy to properly risk stratify these patients, as well as future perspectives on non-invasive techniques, will be addressed.

Quantification of myocardial flow reserve using a gamma camera with solid-state cadmium-zinc-telluride detectors: Relation to angiographic coronary artery disease.

BACKGROUND: Previous studies have suggested using gamma cameras with cadmium-zinc-telluride (CZT) detectors to quantify myocardial blood flow (MBF) and flow reserve (MFR). In this study, we aimed to evaluate the feasibility and accuracy of MFR quantification using a CZT camera compared to coronary angiography. METHODS: Forty-one participants referred for coronary angiography underwent a rest/stress one-day myocardial perfusion imaging protocol using a CZT gamma camera. Rest and stress dynamic phases were followed by acquisition of traditional perfusion images and time-activity curves were generated. Angiographic and perfusion results were compared to MFR. RESULTS: Patients with abnormal perfusion presented reduced MFR (2.01 [1.48-2.77] vs. 2.94 [2.38-3.64], P = 0.002), and reduced stress MBF. Patients with high-risk CAD had lower global MFR compared to patients without obstructive disease (1.99 [1.22-2.84] vs. 2.89 [2.22-3.58], P = 0.026). Obstructed vessels showed lower regional MFR when compared to non-obstructed (1.81 [1.19-2.67] vs. 2.75 [2.13-3.42], P < 0.001). A regional MFR of 2.2 provided a sensitivity of 63.2% and specificity of 74.1% to identify an obstructive lesion in the corresponding artery. CONCLUSION: In patients undergoing invasive coronary angiography for the evaluation of CAD, quantifying MBF and MFR in a CZT gamma camera is feasible and reflects underlying disease. In these patients, reduced regional MFR suggests the presence of obstructive lesion(s).

Enhanced external counterpulsation improves cardiac function in Beagles after cardiopulmonary resuscitation

The aim of this study was to investigate the influence of enhanced external counterpulsation (EECP) on the cardiac function of beagle dogs after prolonged ventricular fibrillation. Twenty-four adult male beagles were randomly divided into control and EECP groups. Ventricular fibrillation was induced in the animals for 12 min, followed by 2 min of cardiopulmonary resuscitation. They then received EECP therapy for 4 h (EECP group) or not (control group). The hemodynamics was monitored using the PiCCO2 system. Blood gas and hemorheology were assessed at baseline and at 1, 2, and 4 h after return of spontaneous circulation (ROSC). The myocardial blood flow (MBF) was quantified by 18F-flurpiridaz PET myocardial perfusion imaging at baseline and 4 h after ROSC. Survival time of the animals was recorded within 24 h. Ventricular fibrillation was successfully induced in all animals, and they achieved ROSC after cardiopulmonary resuscitation. Survival time of the control group was shorter than that of the EECP group [median of 8 h (min 8 h, max 21 h) vs median of 24 h (min 16 h, max 24 h) (Kaplan Meyer plot analysis, P=0.0152). EECP improved blood gas analysis findings and increased the coronary perfusion pressure and MBF value. EECP also improved the cardiac function of Beagles after ROSC in multiple aspects, significantly increased blood flow velocity, and decreased plasma viscosity, erythrocyte aggregation index, and hematocrit levels. EECP improved the hemodynamics of beagle dogs and increased MBF, subsequently improving cardiac function and ultimately improving the survival time of animals after ROSC.

Myocardial blood flow assessment with 82rubidium-PET imaging in patients with left bundle branch block

OBJECTIVES: Perfusion abnormalities are frequently seen in Single Photon Emission Computed Tomography (SPECT) when a left bundle branch block is present. A few studies have shown decreased coronary flow reserve in the left anterior descending territory, regardless of the presence of coronary artery disease. OBJECTIVE: We sought to investigate rubidium-82 (82Rb) positron emission tomography imaging in the assessment of myocardial blood flow and coronary flow reserve in patients with left bundle branch block. METHODS: Thirty-eight patients with left bundle branch block (GI), median age 63.5 years, 22 (58%) female, 12 with coronary artery disease (≥70%; GI-A) and 26 with no evidence of significant coronary artery disease (GI-B), underwent rest-dipyridamole stress 82Rb-positron emission tomography with absolute quantitative flow measurements using Cedars-Sinai software (mL/min/g). The relative myocardial perfusion and left ventricular ejection fraction were assessed in 17 segments. These parameters were compared with those obtained from 30 patients with normal 82Rb-positron emission tomography studies and without left bundle branch block (GII). RESULTS: Stress myocardial blood flow and coronary flow reserve were significantly lower in GI than in GII (p<0.05). The comparison of coronary flow reserve between GI-A and GI-B showed that it was different from the global coronary flow reserve (p<0.05) and the stress flow was significantly lower in the anterior than in the septal wall for both groups. Perfusion abnormalities were more prevalent in GI-A (p=0.06) and the left ventricular ejection fraction was not different between GI-A and GI-B, whereas it was lower in GI than in GII (p<0.001). CONCLUSION: The data confirm that patients with left bundle branch block had decreased myocardial blood flow and coronary flow reserve and coronary flow reserve assessed by 82Rb-positron emission tomography imaging may be useful in identifying coronary artery disease in patients with left bundle branch block.

Estudo comparativo do fluxo da artéria torácica interna utilizada "in situ" na revascularização miocárdica, com e sem a ligadura dos ramos proximais, utilizando a ecocardiografia Doppler / Comparative study of the internal thoracic artery flow used "in situ" for myocardial revascularization, with and without ligation of its proximal branches using Doppler echocardiography

Fundamento: A artéria torácica interna (ATI) "in situ" apresenta predomínio de fluxo sistólico, mas após sua anastomose no sistema coronariano esquerdo torna-se um sistema híbrido com predomínio de fluxo diastólico, sendo a relevância da patência ou não dos grandes ramos proximais da ATI anastomosada controversa quanto à possibilidade de roubo de fluxo. Porém, constata-se que durante o ecocardiograma sob estresse com dobutamina (EED), o estado funcional da ATI anastomosada pode ser avaliado através da reserva coronariana, além da verificação dos distintos efeitos no fluxo sistólico (FS), diastólico (FD) e total (FT = sistólico + diastólico). Objetivo: Verificar por meio da ecocardiografia e Doppler o efeito dos ramos proximais importantes da ATI no fluxo, na reserva de velocidade (RVFC) e de fluxo (RFC) coronariano, em pacientes com fração de ejeção do ventrículo esquerdo (FEVE) preservada (>50%). Métodos: Em ensaio clínico prospectivo controlado e randomizado, foram avaliados pacientes com (Grupo I) e sem (Grupo II), a ligadura dos ramos proximais importantes da ATI anastomosada na coronária descendente anterior. As avaliações das ATIs em nível supraclavicular e os ecocardiogramas transtorácicos foram realizados no pré-operatório, no pós-operatório precoce, seis meses após a cirurgia em condição basal e durante o EED. Neste, foi alcançada a frequência cardíaca submáxima [(220 - idade) x (0,85)] sem a ocorrência de isquemia no território subjacente à ATI anastomosada em todos os pacientes. Foram medidos o FS, o FD, o FT e o percentual de FD, nos quatro momentos do estudo. O percentual de FD resultou da divisão da integral da velocidade diastólica do fluxo pela integral da velocidade total (sistólica + diastólica) do fluxo. A reserva coronariana foi obtida através do Doppler da ATI anastomosada seis meses após a cirurgia, sendo calculada através da razão entre o valor da variável registrado no EED e em condição basal, utilizando-se para as RVFCs o pico e a...

Background: The internal thoracic artery (ITA) "in situ" has systolic flow predominance, but when grafted to the left coronary artery system, the ITA becomes a hybrid system with diastolic flow predominance. The relevance of the patency or not-patency of the large proximal branches of the ITA graft is controversial in regards to the possibility of flow steal. During dobutamine stress echocardiography (DSE), the functional status of the ITA graft can be assessed by the coronary reserve in addition to assessment of the distinct effects of DSE on systolic (SF), diastolic (DF), and total flow (TF = systolic + diastolic). Objective: To assess, by Doppler echocardiography, the effects of the significant proximal branches of ITA graft in the flow, coronary flow velocity reserve (CFVR) and coronary flow reserve (CFR), in patients with preserved (> 50%) left ventricular ejection fraction (LVEF). Methods: In a prospective randomized controlled clinical trial we evaluate patients with (Group I) and without (Group II) ligation of important proximal branches of the ITA grafted to the anterior descending coronary artery. Supraclavicular assessment of the ITAs and transthoracic echocardiograms were performed, at rest and during DSE, on pre-operative, early and six months post-operative. In all patients, the submaximal heart rate [(220 - age) x (0.85)] was achieved during DSE with no ischemia to the area matching the ITA graft. The SF, DF, TF and percentage of DF were measured in the four moments of this study. The percentage of DF was calculated by the ratio of the integral of the diastolic flow velocity by the integral of the total flow velocity (systolic + diastolic). The coronary reserve was assessed at six months post-operative, and it was calculated by the ratio of the variable during DSE and at rest, using the maximum and the mean of the diastolic flow velocity to calculate the CFVR; and the TF to calculate the CFR. Student's t-tests or Wilcoxon's rank sum test (Mann...