cardiology trends and developments

8/13/2019 Cardiology Trends and Developments

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2 MEDICA MUNDI 47/2 August 2003

aim of medical research in the years ahead. Thischange will be supported by improvements in existing imaging techniques, and new developments such asmolecular imaging (See: Medicamundi 2003; 47,1:Special Issue on Molecular Imaging).

The Cardio 2010 project postulates four successivestages of cardiac care, which together provide anintegrated and efficient system of patientmanagement:• screening

• diagnosis & staging • treatment• long-term monitoring.

In this scenario, screening would entail testing largesections of the population for non-symptomaticindications of heart disease. This process needs to beas simple and cost-effective as possible. A simpleblood test, designed to detect indicators of the onsetof cardiac disease, possibly in combination with thepatient’s genetic profile, should be sufficient toidentify individuals who have a high risk of developing cardiac disease. People who test positively in this initial screening process would undergo a further examination at a hospital or dedicated cardiaccare center.

The traditional X-ray based diagnostic imaging methods are increasingly being complemented by other modalities, each with specific strengths andoptions for improving diagnostic accuracy. In

addition to anatomical information such as thestructure of the heart chambers, and the location andcondition of the blood vessels, it is now possible toobtain an increasing amount of functionalinformation, including perfusion and contractionof the myocardium, blood flow in the coronary arteries, and the detection and classification of atherosclerotic deposits.

There has been similar progress in the treatment of cardiac disease. Surgery is becoming less and lessinvasive and has been replaced in many cases by catheter-based interventions. This development issupported by new developments in imaging and

Recent progress in biomedical engineering andimaging technology is providing an ever-increasing body of knowledge on the origins and onset of cardiac disease, with new options for its detectionand treatment (Figure 1). Advances in biomedicalengineering provide new insights, including genomics, proteomics and knowledge of molecularpathways, and enable cell and tissue engineering andnanoinstrumentation. In medical imaging,traditional X-ray angiography has beensupplemented by Computer Tomography (CT),

Magnetic Resonance Imaging (MR), NuclearMedicine (NM) and Echocardiography. In addition,new imaging processing techniques extract a wealthof new visual and quantitative information fromthe acquired image data.

Considerable progress has also been made inelectrophysiology, with increasing use of implanteddevices, and new applications such as treatment of atrial fibrillation by catheter ablation.

The progress in diagnosis and treatment, together with the demands of an aging population, results ina growing requirement for cardiac care, with a corresponding increase in pressure on healthcarebudgets. However, a truly integrated patientmanagement concept should make it possible toprovide improved cardiac care while preventing anexcessive increase in costs.

In an effort to coordinate the industry’s contribution

to rationalizing cardiac care, Philips Medical Systemsand Philips Research launched the Cardio 2010project in 1999. The project brought togethercardiology experts from various branches of PhilipsMedical Systems, as well as specialists from PhilipsResearch. The group also consulted physicians fromseveral leading clinical sites. Together they analyzedtrends and developments in cardiology, and usedthese to sketch out a scenario for the cardiology domain in about 10 years from now.

At present, heart disease is often identified on thebasis of symptoms or an acute event. Shifting detection to as early a stage as possible will be a major

Cardiology: trends and developmentsV. Rasche 1 and G. Gijsbers 2

1Philips Research,Hamburg, Germany.

2Philips MedicalSystems, Best,

the Netherlands.

Progress in

biomedical

engineering and

imaging offers

new insights into

cardiac disease.

Shifting detection

to as early a stage

as possible will be

a major aim in

the years ahead.



MEDICA MUNDI 47/2 August 2003 3

remain more-or-less constant, the aging population will increase the incidence of atrial fibrillation, andthe increased number of heart attack survivors willresult in an increase in the incidence of ischemicventricular tachycardia and the related risks of sudden death.

Coronary artery disease (CAD)

There is already a discernable shift from diagnosing disease at a late stage, after symptoms occur, toasymptomatic diagnosis. Patients at high risk cannow be selected on the basis of risk profiles andscreened in the doctor’s office (Figure 1).

An important recent development is the realizationthat the vast majority of heart attacks are not due toprogressive atherosclerosis, but to sudden ruptureof non-occlusive, vulnerable plaque. Vulnerableplaque consists of an infiltrate of macrophages withina thin fibrous cap overlying a semiliquid lipid core.Rupture of the fibrous cap due to mechanicalstresses such as increased blood pressure releases thelipid and other components into the blood stream,causing thrombosis. Risk stratification strategies forthe prediction of acute coronary syndromes, basedon a comprehensive analysis of the internal andexogenous factors of a given lesion, are therefore of paramount importance.

navigation techniques, with new devices whichenable more complex percutaneous procedures withimproved outcome.

The final stage, long-term monitoring, follows theprogress of disease after treatment, keeping watchover at-risk groups. Care at this stage should be ascomfortable and unobtrusive as possible. It is anti-cipated that remote monitoring or diagnostic devicessuch as wearable ECG recorders and home monitoring services will play an important role in improving the quality of life for chronic cardiac patients.

Cardiovascular diseases

Coronary artery disease (CAD) is still the majorcardiovascular pathology, and is expected to remainso for the foreseeable future. However, improvedtreatment of CAD has resulted in an increasedsurvival rate, so that there is an increasing incidenceof patients with severe myocardial scars caused by previous infarction. These weakened hearts will leadto an increase in the number of patients suffering from congestive heart failure (CHF), who will forman increasingly important group. A third group of patients that is expected to become increasingly important is that of patients with cardiac arrythmias.

While the number of congenital arrythmias will

Figure 1.The role of imagingand non-imagingbiomedical engineeringtechnologies in cardiaccare.

Screening allows

earlier diagnosis,

before symptoms

appear.

Risk stratification

strategies are of

paramount

importance.



apoptosis and viability will become more and moreimportant in selecting the right treatment option.

An increased use of bi-ventricular pacing for

improving cardiac function and implantation of cardioverter defibrillators (ICD) for the reductionof related sudden cardiac death is expected. There

will also be increased use of local myocardialtreatment, such as local delivery of angiogeneticagents or stem cells. The increasing number of CHFpatients is expected to lead to a growth in the use of personal monitoring devices such as automatic ECGrecorders for long-term disease progress monitoring.Since CHF is a chronic disease, comprehensivestandardized patient management approachesensuring optimal delivery of care will gainimportance. There will also be increased use of local myocardial treatment, such as local delivery of angiogenetic agents or stem cells.

Arrhythmias

Treatment of arrhythmias will, to a large extent,remain based on pacemaker implantation forbradycardias, and endocardial mapping of re-entry

circuits and ectopic foci followed by ablation.Percutaneous ablation of areas around the pulmonary veins in the left atrium is an effective procedure forthe treatment of atrial fibrillation in the majority of patients.

Bi-ventricular pacing and implanted defibrillatorsare increasingly being used to treat CHF and ischemicventricular tachycardia, often in the same patient.Implantation of these devices, as well as new devicescombining pacing and defibrillation, will be performedby electrophysiologists in the intervention lab. It isexpected that this type of implantation will becomethe major part of the electrophysiologists’ workload.

Currently, a major part of the diagnosis is based onthe coronary angiogram obtained in the cath lab. Thisis now supplemented by newer imaging modalities

that provide the required information non-invasively.

In future, diagnosis will place more emphasis onfunctional impairment, rather than just on analysisof the coronary anatomy. The importance of thelatter will shift towards treatment and treatmentplanning. Ultimately, conventional imaging-baseddiagnosis may by replaced by molecular imaging andaccess to genetic information.

It is expected that the replacement of open-chestsurgical procedures by less invasive percutaneousapproaches such as percutaneous transluminalinterventions and minimally invasive surgery (MIS)or even endoscopic surgery, will continue.

In percutaneous CAD treatment the trends will betowards more accurate assessment of coronary lesiondimensions, accurate assessment of plaquemorphology and pathology, and more accurateguiding of the intervention device. Drug-eluting

stents are expected to become standard. These stents will reduce in-stent restenosis rates to only a few percent, allowing percutaneous coronary interventionin more complex lesions and multivessel disease.Furthermore, treatment of patients with atheroscleroticdisease by patient-specific drugs is expected toreduce the required number of interventions.

Congestive heart failure (CHF)

The management of CHF patients will demandnew diagnostic and treatment tools. Non-invasiveassessment of the cardiac function in terms of perfusion, local contraction, and myocardial


Figure 2.Rotational angiography shows detailed images of the coronary tree at any desired angle (images reproduced by courtesy of Philips Research, Hamburg).

Diagnosis will

place more

emphasis on

functional

impairment.

Drug-eluting

stents reduce

re-stenosis rates

to only a few

per cent.




Imaging modalities

The traditional techniques of X-ray angiography have now been complemented by a range of imaging modalities, each with its own specific advantagesand applications.

X-ray imaging

X-ray imaging is still the most widely used imaging technique. It provides good spatial resolution (downto about 0.1 mm) and is well suited to guiding interventions. Its main limitations are the need fora contrast agent to enhance the contrast within thearteries and surrounding tissue, and poor imaging of soft tissues. The contrast agent has to be injecteddirectly into the artery, requiring an interventionalprocedure. Important current research work is

focused on rotational angiography (Figure 2), for fastacquisition of large data sets, and 3D and 4D (time-resolved 3D) reconstruction. Image processing methods are also being developed to calculate imagesfrom a limited amount of data, reducing the amountof radiation exposure.

Computed Tomography (CT)

The strong point of CT in cardiology is the fact thatthe entire heart, including the heart chambers andthe coronary arteries and veins, can be covered in a single data acquisition with reasonable spatialresolution within a few seconds (Figure 3). Theresulting 3D or even 4D data sets provide three-dimensional insights into the anatomy (Figure 4).CT is a promising candidate for replacing invasivediagnostic coronary angiography by a non-invasiveprocedure. Currently, its main limitations are thetemporal and spatial resolution, which are stillslightly below those of conventional angiography.

Philips Research is currently working on dedicatedcardiac acquisition and reconstruction algorithms, as well as new detector concepts, in an effort toimprove these points.

Magnetic Resonance (MR) imaging

MR is rapidly gaining ground in cardiac diagnostics(Figure 5). Unlike X-ray, MR provides good contrastbetween different types of soft tissue. This is of value in the detection of vulnerable plaque. MR isthe only technique capable of providing all majorcardiac diagnostic, anatomical and functionalinformation, and is therefore an attractive option for

Figure 4.CT reconstruction:an interior (surgical)view of the left atriumshowing the ostia of the pulmonary veins.

Figure 3.

Volume-rendered view and curved MPR of a reconstructed cardiac 3D volume data set.Reproduced by courtesy of P. Carrascosa, Diagnostico Maipu, Argentina.

Figure 5.

Free-breathing navigator gated coronary MRA of the RCA and LAD acquired with anECG-gated 3D balanced TFE technique. Imaging time for the whole 3D slab (30mm)was approximately 3-4 minutes. There is excellent delineation of both the RCA andLAD. Reproduced by courtesy of Marc Kouwenhoven.



a ‘one-stop shop’ solution. Until recently, however,MR has suffered from limited spatial resolution andrelatively long acquisition times. These issues havebeen addressed by the use of stronger magnetic fields,dedicated detection coils for cardiac measurements,and more efficient data acquisition strategiesincluding parallel acquisition.


Figure 6.Nuclear medicine techniques provide direct evidence of pathological processes. In this example, a human conjugateof Annexin V is labeled with 99mTc to create a molecular probewhich binds to a compound (phosphatidyl serine) exposedin dying cells. The resulting nuclear images show the preciselocation and extent of acute myocardial infarction (AMI)within the myocardium.Reproduced by courtesy of David Rollo.

Figure 6a.The perfusion study, whichdefines normal myocardialtissue, localizes the AMI tothe apical region.

Figure 7.Combined PET and CT image.

Figure 6b.99mTc-Annexin V studyshowing region of celldeath.

Nuclear Medicine imaging

Nuclear Medicine (NM) imaging shows thedistribution of a radioactive substance introducedinto the body. The radioactive substance can be usedto label a molecular imaging agent that will bind toa particular biological molecule, such as phosphatidyl

serine which is released by dying cells. In cases of acute myocardial infarction, the resulting images will show the location and extent of cell death(Figure 6).

Another possible application would be the use of a molecular imaging agent to bind to macrophages inthe fibrous cap of vulnerable plaque, which wouldprovide a valuable early warning system.

At present, nuclear medicine images have poor spatial

resolution and relatively long acquisition times.However, because of their high specificity they areof great value when used in combination with otherimaging modalities (Figure 7). Philips Research iscurrently investigating new detector and systemconcepts for improved sensitivity and spatialresolution, improved motion-compensatedregistration of NM images to CT for bettercorrelation with anatomical details, and improvedreconstruction techniques.

Ultrasound

Ultrasound has undergone rapid development overrecent years. Modern systems can provide real-time3D images, giving a valuable insight into the structureand functioning of organs such as the heart (Figure8). The image data also serves as a basis for quanti-tative analysis, such as the wall-motion analysis andthe quantification of left and right ventricularvolumes, pericardial effusion, intracardiac masses,

defects and endocardial surfaces. Examination of vessel wall motion abnormalities can provide early indication of plaque deposition. Further progress in3D and real-time imaging, and the development of dedicated algorithms, will increase the role of ultra-sound in cardiac diagnostics in the future.

Image processing

Image processing is essential, in order to convert raw imaging data into useful information for thephysician. One of the principal considerations incardiac imaging is heart motion, because the objectchanges location from one image to the next.

MR is an

attractive option

for a ‘one-stop

shop’ solution.




Figure 8.Real-time ultrasoundallows immediateevaluation of thecardiac morphology.This image showsdifferent views of themitral valve and its

subvalvular apparatusacquired via aparasternal echowindow. The papillarymuscle and chordaetendineae are welldefined.LV = left ventricle;LA = left atrium.Reproduced bycourtesy of A. Franke.

Compensating for heart motion by accurate, patient-dependent and location-dependent modeling is animportant topic of research. Several methods are alsobeing investigated for further automation of theextraction of relevant information. One example isa project for automatically rendering the 3D structure

of the arteries from consecutive CT slices, andallowing the path of a given artery to be traced by one movement of a computer mouse. This wouldhelp a physician to prepare an intervention, and helphim or her to navigate during the procedure. Otherprojects are aimed at enhancing the capabilities of the various imaging modalities, for example allowing the walls and the inner surface of the arteries to bedistinguished in MR data for visualization of plaque,and creating properly registered time series foranalyzing perfusion or other dynamic phenomena.

The cath lab of the future

Catheterization is currently performed using real-time X-ray projection imaging. Until recently, theimage receptor has been an image intensifier, butPhilips Research has recently developed new flat-panel detectors that provide better image quality andenable new imaging techniques. These will

undoubtedly find widespread application in thenear future.

3D imaging will become routinely available in thecath lab, in order to support specific steps of theintervention such as treatment planning and

outcome control.

3D intravascular catheter imaging willcomplement guidance of the catheter by X-ray projection imaging.

New techniques are being investigated which willbring dynamic 3D imaging data into theinterventional suite, and which use the additionalinformation obtained from angiographic image data as a ‘roadmap’ for navigation of the catheter during intervention, possibly in combination with activeposition detection techniques attached to the cathetertip. This will improve the accuracy and effectivenessof the procedure, and reduce the amount of contrastagent required.

Application-driven system control and new visualization methods will provide more imageinformation, while reducing X-ray dose still further.

New techniques

will improve the

accuracy and

effectiveness of

catheterization

procedures.

cardiology trends and developments

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