Development and Validation of a New Method to Diagnose Apical Hypertrophic Cardiomyopathy By Gated Single-Photon Emission Computed Tomography Myocardial Perfusion Imaging

Aim The aim of this study is to develop and validate a new method to diagnose apical hypertrophic cardiomyopathy (AHCM) by the integral quantitative analysis of myocardial perfusion and wall thickening from gated single-photon emission computed tomography (SPECT) myocardial perfusion imaging (MPI). Patients and methods Twenty-two consecutive patients, who showed T wave inversion of at least 3 mm in precordial leads and sinus rhythm in ECG, were enrolled. All the patients underwent cardiac magnetic resonance (CMR), gated rest SPECT MPI and echocardiography. According to CMR diagnostic results, 13 patients were categorized as in the AHCM group and the remaining nine patients were categorized as in the non-AHCM group. Operators who were blinded to the CMR diagnosis independently performed the diagnosis by gated SPECT MPI. The regions of interest inside the apical hotspots on the perfusion polar map were drawn and the mean values of wall thickening in the drawn region of interests were calculated. Using MRI diagnosis as the gold standard, AHCM was diagnosed based on receiver operating characteristic analysis of the mean wall thickening in the apical perfusion hotspot. The area under curve, sensitivity, specificity, and accuracy of our method were 0.97, 100, 89, and 95%, respectively. Conclusion Our new method has high sensitivity, specificity, and accuracy against CMR diagnosis. It has great promise to become a clinical tool in the diagnosis of AHCM

Myocardial viability as integral part of the diagnostic and therapeutic approach to ischemic heart failure

Cardiolog

New nuclear medicine techniques for the assessment of myocardial viability

Een dotterbehandeling of een bypassoperatie heeft alleen zin als er nog voldoende hartspierweefsel over is dat zich kan herstellen. Momenteel wordt de vitaliteit van de hartspier voor de ingreep nog onderzocht met een PET-scan, maar deze techniek is duur en maar in een paar ziekenhuizen in Nederland aanwezig. Riemer Slart constateert in zijn proefschrift dat een goedkopere scan het succes van een bypass of dotteren ook kan voorspellen.

Improvements in Cardiac Spect/CT for the Purpose of Tracking Transplanted Cells

Regenerative therapy via stem cell transplantation has received increased attention to help treat the myocardial injury associated with heart disease. Currently, the hybridisation of SPECT with X-ray CT is expanding the utility of SPECT. This thesis compared two SPECT/CT systems for attenuation correction using slow or fast-CT attenuation maps (mu-maps). We then developed a method to localize transplanted cells in relation to compromised blood flow in the myocardium following a myocardial infarction using SPECT/CT. Finally, a method to correct for image truncation was studied for a new SPECT/CT design that incorporated small field-of-view (FOV) detectors. Computer simulations compared gated-SPECT reconstructions using slow-CT and fast-CT mu-maps with gated-CT mu-maps. Using fast-CT mu-maps improved the Root Mean Squared (RMS) error from 4.2% to 4.0%. Three canine experiments were performed comparing SPECT/CT reconstruction using the Infinia/Hawkeye-4 (slow-CT) and Symbia T6 (fast-CT). Canines were euthanized prior to imaging, and then ventilated. The results showed improvements in both RMS errors and correlation coefficients for all canines. A first-pass contrast CT imaging technique can identify regions of myocardial infarction and can be fused with SPECT. Ten canines underwent surgical ligation of the left-anterior-descending artery. Cells were labeled with 111In-tropolone and transplanted into the myocardium. SPECT/CT was performed on day of transplantation, 4, and 10 days post-transplantation. For each imaging session first-pass perfusion CT was performed and successfully delineated the infarct zone. Delayed-enhanced MRI was performed and correlated well with first-pass CT. Contrast-to-noise ratios were calculated for 111In-SPECT and suggested that cells can be followed for 11 effective half-lives. We evaluated a modified SPECT/CT acquisition and reconstruction method for truncated SPECT. Cardiac SPECT/CT scans were acquired in 14 patients. The original projections were truncated to simulate a small FOV acquisition. Data was reconstructed in three ways: non-truncated and standard reconstruction (NTOSEM), which was our gold-standard; truncated and standard reconstruction (TOSEM); and truncated and a modified reconstruction (TMOSEM). Compared with NTOSEM, small FOV imaging incurred an average cardiac count ratio error greater than 100% using TOSEM and 8.9% using TMOSEM. When we plotted NTOSEM against TOSEM and TMOSEM the correlation coefficient was 0.734 and 0.996 respectively

Left ventricular remodeling and function in ischemic heart disease and aortic valve disease

Background: Cardiac remodeling is a broad term that refers to structural and functional alterations of the heart in response to chronic changes in loading conditions or left ventricular (LV) contractile performance. Different loading conditions will affect the heart in different ways, some leading to impaired heart function, symptoms of heart failure, or even death. However, the process of remodeling may not be permanent. If the heart is relieved of the underlying cause of the remodeling, the heart function and structure may normalize in a process referred to as reverse remodeling. The complex interplay of factors that determine the process of reverse remodeling is not fully elucidated. Cardiac remodeling can be evaluated by many different diagnostic modalities, but the most widely used diagnostic tool is two-dimensional echocardiography (2DE). In recent years, three-dimensional echocardiography (3DE) has emerged with possible advantages in the assessment of LV volume and function. The thesis aimed to evaluate 3DE in the assessment of LV function and remodeling, and to study different aspects of remodeling in response to pressure and volume overload in patients with aortic stenosis (AS) and aortic regurgitation (AR), respectively. Methods: Studies I and II investigated patients with ischemic heart disease (n = 15 and n = 32, respectively). In Study I, the assessments of LV volume and ejection fraction (EF) were compared using 3DE, cardiac magnetic resonance (CMR), and single-photon emission computer tomography (SPECT). Study II compared the performance of 2DE, contrast-enhanced 2DE, 3DE, and contrast-enhanced 3DE in the assessment LV volumes and EF, using CMR as a reference standard. In Studies III and IV, 65 patients with severe AR and 120 patients with severe AS, respectively, were examined using 2DE and 3DE before and at one year after aortic valve replacement (AVR). In Study III, LV volumes, systolic and diastolic LV function, and left atrial strain (LAS) were analyzed to identify predictors of impaired LV reverse remodeling in AR. Study IV assessed LV functional indices, including 2D global longitudinal strain (GLS) and 3D strain, to assess predictors of incomplete reverse remodeling in AS. Results and conclusions: There were significant differences among 3DE, SPECT and CMR regarding the measurement of LV volumes. However, the estimation of EF showed good agreement. 3DE was more accurate and showed more favorable reproducibility than 2DE for the assessment of EF and LV volumes. Contrast enhancement improved accuracy and reproducibility for both 2DE and 3DE. One-third of patients with AR had signs of impaired LV diastolic function. After AVR, diastolic LV functional indices improved, LV and left atrial (LA) volumes decreased, and indices of LA function increased. LA conduit strain had an incremental prognostic value for the prediction of impaired LV functional and structural recovery. In patients with AS, AVR was associated with a decrease in LV mass, an improvement in 2D GLS, and a decrease in LV twist. 2D GLS and left ventricular mass index were predictive of incomplete reverse remodeling during the follow-up period. 3D GLS did not add discriminatory or predictive information over 2D GLS

Data registration and fusion for cardiac applications

The registration and fusion of information from multiple cardiac image modalities such as magnetic resonance imaging (MRI), X-ray computed tomography (CT), positron emission tomography (PET) and single photon emission computed tomography (SPECT) has been of increasing interest to the medical community as tools for furthering physiological understanding and for diagnostic of ischemic heart diseases. Ischemic heart diseases and their consequence, myocardial infarct, are the leading cause of mortality in industrial countries. In cardiac image registration and data fusion, the combination of structural information from MR images and functional information from PET and SPECT is of special interest in the estimation of myocardial function and viability. Cardiac image registration is a more complex problem than brain image registration. The non-rigid motion of the heart and the thorax structures introduce additional difficulties in registration. In this thesis the goal was develop methods for cardiac data registration and fusion. A rigid registration method was developed to register cardiac MR and PET images. The method was based on the registration of the segmented thorax structures from MR and PET transmission images. The thorax structures were segmented from images using deformable models. A MR short axis registration with PET emission image was also derived. The rigid registration method was evaluated using simulated images and clinical MR and PET images from ten patients with multivessel coronary artery diseases. Also an elastic registration method was developed to register intra-patient cardiac MR and PET images and inter-patient head MR images. In the elastic registration method, a combination of mutual information, gradient information and smoothness of transformation was used to guide the deformation of one image towards another image. An approach for the creation of 3-D functional maps of the heart was also developed. An individualized anatomical heart model was extracted from the MR images. A rigid registration of anatomical MR images and PET metabolic images was carried out using surface based registration, and the registration of MR images with magnetocardiography (MCG) data using external markers. The method resulted in a 3-D anatomical and functional model of the heart that included structural information from the MRI and functional information from the PET and MCG. Different error sources in the registration method of the MR images and MCG data was also evaluated in this thesis. The results of the rigid MR-PET registration method were also used in the comparison of multimodality MR imaging methods to PET.reviewe

Sepelvaltimotaudin noninvasiivinen tutkiminen

Conventional invasive coronary angiography is the clinical gold standard for detecting of coronary artery stenoses. Noninvasive multidetector computed tomography (MDCT) in combination with retrospective ECG gating has recently been shown to permit visualization of the coronary artery lumen and detection of coronary artery stenoses. Single photon emission tomography (SPECT) perfusion imaging has been considered the reference method for evaluation of nonviable myocardium, but magnetic resonance imaging (MRI) can accurately depict structure, function, effusion, and myocardial viability, with an overall capacity unmatched by any other single imaging modality. Magnetocardiography (MCG) provides noninvasively information about myocardial excitation propagation and repolarization without the use of electrodes. This evolving technique may be considered the magnetic equivalent to electrocardiography. The aim of the present series of studies was to evaluate changes in the myocardium assessed with SPECT and MRI caused by coronary artery disease, examine the capability of multidetector computed tomography coronary angiography (MDCT-CA) to detect significant stenoses in the coronary arteries, and MCG to assess remote myocardial infarctions. Our study showed that in severe, progressing coronary artery disease laser treatment does not improve global left ventricular function or myocardial perfusion, but it does preserve systolic wall thickening in fixed defects (scar). It also prevents changes from ischemic myocardial regions to scar. The MCG repolarization variables are informative in remote myocardial infarction, and may perform as well as the conventional QRS criteria in detection of healed myocardial infarction. These STT abnormalities are more pronounced in patients with Q-wave infarction than in patients with non-Q-wave infarctions. MDCT-CA had a sensitivity of 82%, a specificity of 94%, a positive predictive value of 79%, and a negative predictive value of 95% for stenoses over 50% in the main coronary arteries as compared with conventional coronary angiography in patients with known coronary artery disease. Left ventricular wall dysfunction, perfusion defects, and infarctions were detected in 50-78% of sectors assigned to calcifications or stenoses, but also in sectors supplied by normally perfused coronary arteries. Our study showed a low sensitivity (sensitivity 63%) in detecting obstructive coronary artery disease assessed by MDCT in patients with severe aortic stenosis. Massive calcifications complicated correct assessment of the lumen of coronary arteries.Sepelvaltimotaudin noninvasiivinen tutkiminen Perinteinen sepelvaltimoiden varjoainekuvaus on ollut kulmakivi sepelvaltimotaudin tutkimisessa. Kuitenkin pieni vakavien komplikaatioiden riski, tutkimuksen epämukavuus ja sairaalahoitopäivät potilaalle ovat johtaneet potilaasta vähemmän rasittavien, noninvasiivisten, tutkimusmenetelmien etsimiseen. Sydämen noninvasiivisen tutkimisen mahdollisuudet ovat kehittyneet viime vuosina huimaa vauhtia. Tutkimuksessa selvitettiin sydämen isotooppitutkimuksen lisäksi uusien tutkimusmenetelmien, monileiketietokonetomografian, magneettikuvauksen ja magnetokardiografian, käyttökelpoisuutta sepelvaltimotaudin eri ilmentymien tutkimisessa. Sepelvaltimoiden tietokonetomografia on uusi lupaava menetelmä sepelvaltimoahtaumien, kalkkikertymien ja pehmeiden plakkien tutkimisessa. Magneettikuvauksella voidaan arvioida sydänlihaksen toimintaa ja mahdollisia infarktialueita. Monikanavainen magnetokardiografia antaa tarkkaa tietoa sydämen sähköisestä toiminnasta. Tutkimukseen osallistui 43 eriasteista sepelvaltimotautia, 23 aorttaläpän ahtaumaa sairastavaa potilasta ja 26 tervettä verrokkihenkilöä. Tutkimuksessa todettiin, että sydänlihaksen laserkanavointi pitkälle edenneessä sepelvaltimotaudissa ei parantanut sydänlihaksen pumppaus- tehokkuutta eikä sydänlihaskudoksen verenvirtausta, joita mitattiin magneetti- ja isotooppikuvauksella. Laserkanavointi näytti 6 kk:n seurannassa kuitenkin hidastavan sydänlihaksen pysyvien vaurioiden syntyä. Yhdistämällä informaatiota sydämen magneettikuvauksesta ja sepelvaltimoiden monileiketietokonetomografiasta, totesimme että sydämen seinämän liikehäiriöitä, verenvirtauspoikkeavuuksia ja infarkteja oli myös alueilla, joiden sepelvaltimoissa ei todettu mitään poikkeavaa. Tietokonetomografian osuvuus perinteiseen varjoainekuvaukseen verrattuna on varsin hyvä, mutta aorttaläpän ahtaumaa sairastavilla potilailla runsaat kalkkikertymät vaikeuttivat sepelvaltimoahtaumien löytymistä. Monikanavaisen magnetokardiografia osuvuus perinteiseen 12-kytkentäiseen EKG:hen ja magneettikuvaukseen sydäninfarktiarpien osoittamisessa todettiin hyväksi sekä Q- että non-Q-aalto infarkteissa. Noninvasiivisten tutkimusmenetelmien käyttö tulee lisääntymään laitteiden kehittyessä nopeasti. Monileiketietokonetomografia sepelvaltimoiden kuvantamisessa voi osalla potilaista korvata perinteisen sepelvaltimoiden varjoainekuvauksen. Myös magneettikuvauksen antamat mahdollisuudet sydänlihaksen toimintahäiriöiden ja infarktien kuvantamisessa sopivat enenevässä määrin kliiniseen käyttöön

Feasibility and diagnostic power of transthoracic coronary Doppler for coronary flow velocity reserve in patients referred for myocardial perfusion imaging

<p>Abstract</p> <p>Background</p> <p>Myocardial perfusion imaging (MPI), using single photon emission computed tomography (SPECT) is a validated method for detecting coronary artery disease. Transthoracic Doppler echocardiography (TTDE) of flow at rest and during adenosine provocation has previously been evaluated in selected patient groups. We therefore wanted to compare the diagnostic ability of TTDE in the left anterior descending coronary artery (LAD) to that of MPI in an unselected population of patients with chest pain referred for MPI. Our hypothesis was that TTDE with high accuracy would identify healthy individuals and exclude them from the need for further studies, enabling invasive investigations to be reserved for patients with a high probability of disease.</p> <p>Methods</p> <p>Sixty-nine patients, 44 men and 25 women, age 61 ± 10 years (range 35–82), with a clinical suspicion of stress induced myocardial ischemia, were investigated. TTDE was performed at rest and during adenosine stress for myocardial scintigraphy.</p> <p>Results</p> <p>We found that coronary flow velocity reserve (CFVR) determined from diastolic measurements separated normal from abnormal MPI findings with statistical significance. TTDE identified coronary artery disease, defined from MPI, as reversible ischemia and/or permanent defect, with a sensitivity of 60% and a specificity of 79%. The positive predictive value was 43% and the negative predictive value was 88%. There was an overlap between groups which could be due to abnormal endothelial function in patients with normal myocardial perfusion having either hypertension or diabetes.</p> <p>Conclusion</p> <p>TTDE is an attractive non-invasive method to evaluate chest pain without the use of isotopes, but the diagnostic power is strongly dependent on the population investigated. Even in our heterogeneous clinical cardiac population, we found that CFVR>2 in the LAD excluded significant coronary artery disease detected by MPI.</p