A cardiovascular treatment method utilizes an elongate flexible surgical instrument (e.g., catheter) having a distal end. A distal end portion of the instrument is inserted into a vascular system of a patient. A surgical head at the distal end of the instrument is positioned so that the head is disposed adjacent to myocardium tissue of the patient. The head is operated to form a recess in the myocardium tissue. Prior to operating the head to form the recess, a thickness of the myocardium tissue is measured, the recess formed during the operation having a length determined in accordance with the measured thickness of the myocardium tissue. The thickness measurement partially determines the length of the recess. The angle of entry of the recess with respect to the heart wall also partially determines the length of the recess: the greater the angle, the longer the recess can be for a given myocardium thickness.

Coronary artery by-pass method

A medical probe includes a flexible insertion tube, having a distal end for insertion into a body cavity of a patient, and a distal tip, which is disposed at the distal end of the insertion tube and is configured to be brought into contact with tissue in the body cavity. A resilient member couples the distal tip to the distal end of the insertion tube and is configured to deform in response to pressure exerted on the distal tip when the distal tip engages the tissue. A position sensor within the probe senses a position of the distal tip relative to the distal end of the insertion tube, which changes in response to deformation of the resilient member.

Catheter with pressure sensing

A mapping and ablation catheter with contact force sensing capabilities at a distal end, includes a catheter body, a deflectable section, and a tip distal section which has a tip electrode and a contact force sensor for sensing a 3D contact force vector applied to the tip electrode. In contact with the tip electrode, the contact force sensor has a body and has at least one sensor with an electrical characteristic that is responsive to deformation of the body resulting from force vector. The sensor is adapted to receive an electrical current and to output an electrical signal indicative of a change in the electrical characteristic. In one embodiment, the sensor is a strain gage responsive to tension and compression of at least a portion of the body of the force sensor and the electrical characteristic of the strain gage that is monitored is electrical resistivity. In another embodiment, the sensor is responsive to strain and stress of at least a portion of the body, and the electrical characteristic being monitored is inductance or hysteresis loss.

Catheter having a force sensing distal tip

This apparatus is adapted for replaceable implantation in soft body tissues for the measurement of the mechanical behavior of the soft tissues of the body. The apparatus consists of a thin walled tube containing a longitudinal slot down one side with at least one piezo-resistive strain gauge element bonded to its inner or outer walls. Tension in tissue fiber bundles results in a squeezing pressure against the sides of the tube, which produces a change in the shape of the tube and thus a change in the resistance of the strain gauge element. This resistance change is then measured and displayed. A method of inserting and removing the apparatus is also described, as are several techniques for calibration.

Method of and means for implanting a pressure and force sensing apparatus

A set of electrodes are provided, preferably in a symmetrical array, which electrodes are mounted within a pliable mounting cup that is capable of conforming to the shape and size of various surfaces of body organs, such as the heart. The pliable cup is capable of both epicardial and endocardial types of mapping procedures, each electrode being connected to a thin insulated wire that joins similar wires in a generally centrally located trunk portion of the cup, and a cable containing the thus bundled wires depends from the trunk portion for connection to a suitable data display and/or recording system.

Mapping electrode assembly

A force transducer for measuring dynamic force activity within the heart of a subject essentially consists of a U-shaped beam of low elastic compliance material. Two tines extend from the beam's legs and a long coil spring is attached to the beam. A strain gauge is coupled to one of the beam's legs to sense deflections thereof. The beam with the tines and most of the spring are surrounded by a flexible tube, defining a catheter, which is insertable into a subject's heart through an appropriate artery. The tines are extractable from the catheter for implantation into the myocardium by pushing on the end of the spring which extends beyond the external end of the catheter. The tines are retractable back into the catheter, prior to catheter removal from the subject, by pulling on the externally exposed spring end.

/pdf/catheter-tip-force-transducer-for-cardiovascular-research-3c8ag434re.pdf

Catheter tip force transducer for cardiovascular research

A myocardial transducer for simultaneously measuring force and displacement within a very small area of myocardium comprising an elongated body forked at one end to form an inverted Y-shaped beam, each branch of the beam constituting a low-compliant tine for penetrating the myocardium to a predetermined depth. Each tine has a transverse indentation formed around at least a part of it. When the tines are inserted into a heart, the surface membrane of the myocardium closes around the indentations to hold the tines in place. Bonded to one of the low-compliance tines is a small piezoresistive element for converting a force acting on the beam into an electrical signal. A third high-compliant tine of the transducer, which measures displacement of the myocardium in a direction in line with the two low-compliant tines, is of a length that just pierces the surface membrane. A small piezoresistive element is bonded to the third tine at its upper end where its bending is greatest. Displacement of the myocardium causes a deformation in curvature of the third tine, and the second small piezoresistive element bonded to the surface of its curved end converts its deformation into an electrical signal. A separate electrode placed on the epicardium and referenced to the transducer body provides an ECG signal simultaneously with force and displacement signals.

/pdf/simultaneous-muscle-force-and-displacement-transducer-3lrh5ahp6k.pdf

Simultaneous muscle force and displacement transducer

A myocardium wall thickness measuring transducer comprises a circular beam of high compliance and an elongated spike which extends in the plane in which the beam is disposed. The spike is connected at one point to the beam while a working end of the spike to which a barb is attached, extends through an opening in the beam at a substantially diametrically opposite point. The beam portion, surrounding the opening, is free to move or be displaced relative to the spike. A sensitive strain gauge is bonded to the beam to sense changes in the tension thereof. The working end of the spike is inserted through the epicardium into the myocardium so that the spike and the beam are in a plane substantially perpendicular to the epicardium at the point of insertion. The spike is inserted, to a depth at which a minimal beam deforming force is applied by the myocardium to the beam portion surrounding the opening. As the heart contracts and myocardium thickness increases larger beam-deforming forces are applied to the beam which increase the beam tension, which is sensed by the strain gauge whose changing output is supplied to an appropriate recorder.

https://ntrs.nasa.gov/api/citations/19760022807/downloads/19760022807.pdf

Virgil H. Culler

Papers

Catheter tip force transducer for cardiovascular research

Simultaneous muscle force and displacement transducer

Myocardium wall thickness transducer and measuring method