TTK CHITRA VALVE

• Materials of Construction•

The three main components of TTK Chitra Heart Valve are:• Frame• Disc• Sewing Ring

• Tilting Disc– pivoted eccentrically in the metallic frame.– MADE FROM ULTRA HMW POLY ETHYLENE

• The sewing ring– POLYETHYLENE TEREPTHALATE (PET)– fitted snugly around the frame– used to suture the valve in the intended position in the

heart.FRAME: COBALT CHROMIUM ALLOY( HAYNES 25)

• The frame and the disc are hydro dynamically designed to reduce drag and inertia and polished to minimize the chances of clotting.

Salient Features

• Complete Structural Integrity• Absence of cavitation related damage.• Silent operation• Rotatable within the sewing ring to assure its

freedom to rotate if repositioning is required• Low profile

CHALLENGES

• In 1976, with a project funded by the Department of Science and Technology,

• M.S. Valiathan initiated efforts to make heart valves within the country.

• Four years later, the Institute, which had been started by the Kerala Government, was taken over by the Central Government.

• The artificial valve must withstand the stress of opening and closing some 40 million times a year.

• The materials used for the valve have to be compatible with blood and human tissues.

• When open, the valve should allow the blood to flow smoothly through.

• Once closed, the back flow of blood had to be minimal.

• In the first model, • the major and minor struts were electron beam welded and the

valve was expected to withstand 360 million cycles of disc movement.

• Unfortunately, the major strut fractured at the weld after a mere 100,000 cycles due to weld embrittlement.

• In the second model, the disk was made of single crystal sapphire which was inert and blood compatible.

• The housing was carved out of a block of titanium.

• This model failed as well, because of the extensive wear of titanium struts and the escape of the disc.

• The third model had a housing made of a• highly wear – resistant aerospace superalloy, called "Haynes-25",

a cobalt based alloy of chromium, nickel and tungsten.

• This model went through all the tests successfully and several sheep with the implanted valve were alive and well for months

• until the death of one animal at 3 months after valve implantation.

• Necropsy showed that the sapphire disc had fractured in the animal.

• This was a major crisis as critics and media did not spare the team• and the search for a material to replace it had to start a new.

Mile Stones

• The first human implant was December 6, 1990 at Sree Chitra Tirunal Institute for Medical Sciences and Technology, Trivandrum.

• In Clinical use for over 14 years.

• More than 55,000 TTK Chitra Heart Valve has been implanted so far in India, Nepal, Sri Lanka, Bangladesh and South Africa, Thialand

• Crossed over 1,00,000 patient years• Award for TTK Chitra heart valve prosthesis

Hinduonnet

• Award for TTK Chitra heart valve prosthesisMay 17, 2001, Medindia

• TTK Chitra Heart Valves bagged the following patents

• US patent No.5,458,826 dated October 17, 1995 for the "method of producing a heart valve disc" - one of the three major component of this critical, life saving device

• European patent No.0622060 relating to "Improvement in or relating to Prosthetic Cardiac Valve and to the method of manufacturing same“

• Nearly 250 centres using TTK Chitra Heart Valves.

• More than 300 Surgeons using our valves

Trial And Evaluation• Invitro Evaluation• A specially designed computerized accelerated durability test system is used to

validate the mechanical performance

• and wear of the valve in simulated use conditions for above 380 million cycles - which is equal to 10 years in actual use.

• is also tested for its haemodynamic performance, which is an important factor in artificial heart valves.

• A comprehensive evaluation is also done through a computerized special purpose pulse duplicator and steady state and dynamic measurements are made for all sizes of the valve.

• The results of all the tests conducted are comparable with the best international brands of mechanical Heart Valves

• and the TTK Chitra Heart Valve has been proven to equal the best international brand of mechanical heart valves.

Biocompatibility Evaluation

• All the materials used in the valve have undergone extensive toxicological and implant evaluation that is applicable to permanent implants.

• As per the ISO protocol for artificial heart valves, the TTK Chitra Heart Valve has passed through rigorous in vivo animal trials in sheep.

• During the trial, the valves were implanted in the mitral position without any anticoagulation regimen for the animals.

• The long time survival of these animals even under these difficult conditions was uneventful.

Clinical Trials• Based on the data obtained from the evaluations and trials,• the ethics committee of the Sree Chitra Tirunal Institute for Medical

Sciences and Technology, Trivandrum, • chaired by a sitting judge of a high court of the land gave formal permission

for controlled clinical trials in 1990.

• The TTK Chitra Heart Valve was implanted in a human for the first time in December 1990.

• Six institutions in India took part in a multicentric trial that lasted till 1995.• N= 306• The trials were monitored by a national level monitoring committee,• and the results were periodically presented at the annual conference of the

society of the Indian Association of Cardiovascular Thoracic Surgeons.

• The ethics committee cleared the valve for commercial production during 1995.

Pressure Recovery:Hemodynamic Conditions and Clinical Implications. • can occur in two regions:– downstream of a valve• flow expands into the wider lumen beyond a valve, velocity

and kinetic energy will decrease and pressure will be recovered

– within some prosthetic valves, typically bileaflet or caged-ball valves

•The smaller central orifice in bileaflet valves may give rise to a high-velocity jet • that corresponds to a localized pressure drop• that is largely recovered once the central flow reunites with flows originating from two lateral orifices

Velocity and Gradients. • Resemble those of mild native aortic stenosis• maximal velocity usually >2 m/s• Triangular shape of the velocity contour• occurrence of the maximal velocity in early systole. • Short AT

• High gradients may be seen with normally functioning valves with• a small size, • increased stroke volume, • PPM,• valve obstruction.

• Conversely, a mildly elevated gradient in the setting of severe LV dysfunction

• may indicate significant stenosis.

• AT: the time from the onset of flow to maximal • NORMAL: AT < 100MSECS• AT/ET < .04

• EOA:

DVI

• DVI is a dimensionless ratio of• the proximal velocity in the LVO tract to that

of flow velocity through the prosthesis:DVI = V LVO / V PrAV

• much less dependent on valve size.• HELPFUL when the CSA of the LVOT cannot be

obtained or valve size is not known.

PROSTHETIC MV

• There were 200 patients, 118 males and 82 females, who received 249 TTK Chitra valve implants in the mitral and/or aortic position

• The mean duration of followup was 2.5 years (range 1 month to 4.5 years)• minimum follow-up of survivors was 1 year, and the total follow-up

observed was 451 patient-years (pt-yr).

• Assesed relative risk associated with 6 factors• age, sex, • Preoperative NYHA class• primary valve lesion • Preoperative atrial fibrillation and CCF

Early mortality was low in all 3 groups

• there were 3 (1.5%) deaths overall.

• MVR group 2– valve thrombosis – intractable ventricular arrhythmias.

• DVR group 1– due to myocardial dysfunction. These patients were in an advanced NYHA class of disability

preoperatively.

• Late deaths occurred in 18 patients (4.0% 0.9%/ptyr)

CONCLUSIONS

• The striking features • The patient profile in our study are the young age

(mean 28.9 years) • advanced disability (75.6% in NYHA classes III and IV).

• Postoperative conversions to a lower NYHA class were evident.

• The gradients for various valve sizes were found to be comparable to those of other widely used valves

• The absence of any reports of paravalvular leak or discomfort due to valve sounds is a notable feature of the Chitra heart valve.

• The closing sounds are soft and dull due to the use of an ultra-high molecular weight polyethylene disc.

• This was clearly highlighted by the pressure field and cavitation measurements of Chandran and colleagues at the University of Iowa,

• They studied the in-vitro and in-vivo closing dynamics of the current clinical models of mechanical heart valves, including the Chitra heart valve.

• While the in-vitro studies showed an absence of cavitation even at the highest valve closing rates,

• the in-vivo tests demonstrated that the negative transients were relatively low and did not reach magnitudes close to the vapor pressure for the fluid

• Therefore, compared to valves with rigid occluders, in-vivo cavitation is regarded as unlikely.

• CHV (n=65) • between January 1992 and December 1995• Forty three patients FOLLOWED UP.• The age ranged from 8 to 62 yrs. • The male to female ratio was 1.6:1

• No structural complications were noted in this group of patients.

• Conclusion CHV has good haemodynamics with no structural

MORTALITY 20 % 9

VALVE THROMBOSIS

4.6 % 2

I/E 4.6% 2

MI 2.3% 1

LV DYSFUNC 2.3% 1

UNKNOWN 6/9 3

CONCLUSIONS

• No structural deterioration• Good hemodynamics and• Acceptable thrombo-embolic events.• LOW COST

• to determine the normal Doppler parameters of CHVP in the mitral position

• and to assess whether derivation of MVA using the CE and PHT method is comparable in the functional assessment.

• 40 consecutive patients• Indications – RHD 95% (38 patients)– MVP in 5% (2 patients).

Doppler evaluation of mitral prostheses

• Early velocity• peak gradient• mean gradient• MVA derived by PHT and the CE.• The actual orifice area • (AOA) is calculated from the valve orifice

diameter (VOD) provided by the manufacturer as • AOA = 0.785 X VOD2

• Mean and peak gradients did not show significant correlation with MVA by PHT .

• Similarly, no correlation was noted between meanand peak gradients and MVA by the CE.

• Peak gradient did not correlate well with AOA

• However, the mean gradient decreased significantly with an Increase in the AOA.

• The MVA calculated by both PHTand CE increased significantly with an increase in the AOA

• The MVA by PHT showed a significant linear correlation

– with MVA derived by CE (r ¼ 0.041, P ¼ 0.009)

– tends to be higher than that calculated by the CE,

– and this difference was statistically significant (P , 0.001, t-test).

• This difference was irrespective of whether PHT is > or<110 ms

• The subgroup analysis between groups with PHT is > or<110 ms

– showed no difference in the mean or peak mitral gradients.

– Calculation by CE also showed no difference for calculated MVA between the two groups.

• Our study also showed significant correlation between the valve area derived by CE and AOA, similar to published studies of other valves.

547 consecutive patients, 310 males 237 females 634 implants with the TTK Chitrain mitral and/ or aortic positions.

Age -9 years to 64 years (mean age = 26±5 years).

PREOPERATIVE DATA

• NYHA CLASS• II 238• III 235• IV 74

• NSR 233• AF 314

• PREVIOUS PROCEDURE• PTMC 80• OMC 6• BIOPROS VALVE 8• (MVR 6, AVR 2)

• ADDED SURGERY• ASD CLOSURE 20• TV REPAIR 47• CAD 4

E ARLY DEATH < 30 DAYS NO PERCENTAGEMVR 7 1.25AVR 4 1.4DVR 1 1

REXPLORATION 15 2.6

502 PTS 93% CAME FOR F/UPERIOD 120-990 DAYSMEAN 416+184

NO STRUCTURAL VALVE DETORIATION

NYHA CLASS I 391 78%NYHA CLASS II 80 16%NYHA CLASS II 31 6.2%

LINEARISED RATE MAJOR HEMORRAGE

TEE

MVR 1 % 3.8%

AVR 2.1% 2.1%

DVR 1.75% 3.7%

(Ind J Thorac Cardiovasc Surg, 2005; 21: 15–17)

• G.K.N.M. Hospital, Coimbatore

• Initially this valve was used as part of a multi-centric trial and later it was the valve of choice in our institution.

• Methods• December 1992 and July 1998 -- a total of 152 Chitra

Valve

• 65 aortic and 64 mitral implants and the rest were dou b le valves.

• 144 patients were followed up ( 10 EARLY DEATHS)• (a total of 622 patient years of follow-up) • There were 11 patients (7.2%) TEE• (5 major events)• a linearized rate of 1.8 percent patient year.• Haemodynamic studies in postoperative patients were

comparable to other prosthetic valves.

• The thrombo-embolism free survival was 82% at 5 years. The actuarial survival was 78% at 5 years.

• Conclusion• The Chitra valve is comparable to other mechanical valves

THANK YOU

Conclusion: At 20 years the Medtronic Hall valve demonstrates excellent durability, good hemodynamic performance, and very low thrombogenicity, with a valve thrombosis rate lower than those reported for bileaflet designs. With this prosthesis, both survival and thromboembolic events are predominantly determined by patient risk factors.(J Thorac Cardiovasc Surg 2001;121:1090-100)

• Objective: To assess the performance of the Medtronic Hall valve (Medtronic, Inc, Minneapolis, Minn) in one institution over a 20-year period.

• Methods: Since 1979, Medtronic Hall valves have been used in 1766 procedures (736 aortic, 796 mitral, and 234 double). Patients were followed up prospectively at 6- to 12-month intervals for a total of 12,688 follow-up years. Anticoagulation data (international normalized ratio) were recorded for all patients (approximately 95,000 observations).

• Results: Linearized rates of valve-related late death for aortic, mitral, and double valve replacement were 0.8%/y, 0.9%/y, and 1.1%/y, respectively. Risk factors for late mortality were (relative risk) diabetes (1.9), decade of age (1.6), concomitant coronary artery bypass grafting (1.4), hypertension (1.3), non-sinus rhythm (1.3), large valve size (1.1), valve regurgitation (1.3), and male sex (1.2). For aortic, mitral, and double valve replacement, linearized rates (percent per year) of adverse events were valve thrombosis 0.04, 0.03, and 0.0; all thromboembolism 2.3, 4.0, and 3.4; stroke 0.6, 0.8, and 0.6; major hemorrhage 1.2, 1.4, and 1.6; and prosthetic endocarditis 0.4, 0.4, and 0.7. Risk factors for thromboembolism were (relative risk) mitral valve replacement (1.9), diabetes (1.8), hypertension (1.5), and history of embolism (1.4).

• Tilting disk valves have separate projections into the orifice, either single arms or closed loops to retain and guide the disk-shaped occluder.

• Among the metals use for the housing are stainless steel and titanium.

• The disks are graphite with a coating of pyrolitic carbon.

• The Bjork-Shiley valve was the first successful tilting valve.

• It became available in 1971 with a carbon-coated disk and both struts (inflow and outflow) welded to the chromium alloy orifice.

• The Medtronic Hall valve has a titanium housing machined from a solid cylinder and a thin carbon coated disk with flat parallel sides

• The Omniscience valve is a streamlined elegant looking valve. It has a curved pyrolitic Carbon disk with no indentations, a one- piece titanium cage, and a seamless polyester knit sewin ring.