Patent Description:
Cardiac pacing by an artificial pacemaker provides an electrical stimulation of the heart when its own natural pacemaker and/or conduction system fails to provide synchronized atrial and ventricular contractions at rates and intervals sufficient for a patient's health. Such antibradycardial pacing provides relief from symptoms and even life support for hundreds of thousands of patients. Cardiac pacing may also provide electrical overdrive stimulation to suppress or convert tachyarrhythmias, again supplying relief from symptoms and preventing or terminating arrhythmias that could lead to sudden cardiac death.

Leadless cardiac pacemakers incorporate electronic circuitry at the pacing site and eliminate leads, thereby avoiding shortcomings associated with conventional cardiac pacing systems. Leadless cardiac pacemakers can be anchored at the pacing site, e.g., in a right ventricle and, for dual-chamber pacing, in a right atrium, by an anchor. <CIT> discloses extraction devices for extracting chronically implanted devices such as leadless cardiac pacemakers. <CIT> discloses systems for positioning a leadless pacing device in cardiac tissue. <CIT> discloses systems for delivering and retrieving a leadless pacemaker. A delivery system can be used to deliver the leadless cardiac pacemakers to the target anatomy. <CIT>, <CIT> and <CIT> disclose delivery tools for implantable medical devices.

Cardiac pacing of the His-bundle is clinically effective and advantageous by providing a narrow QRS affecting synchronous contraction of the ventricles. His-bundle pacing in or near a membranous septum of a heart, however, has some drawbacks. The procedure is often long in duration and requires significant fluoroscopic exposure. Furthermore, successful His-bundle pacing cannot always be achieved. Pacing thresholds are often high, sensing is challenging, and success rates can be low.

Pacing at the left bundle branch (LBB) is an alternative to His-bundle pacing. Pacing at the LBB involves pacing past the His-bundle toward the right ventricle apex. More particularly, a pacing site for LBB pacing is typically below the His-bundle, on the interventricular septal wall near the tricuspid valve and pulmonary artery outflow track.

Existing leadless pacemakers may not fit, or may interfere with heart structures, when placed at a pacing site for left bundle branch (LBB) pacing. More particularly, existing leadless pacemakers have bodies that are long and rigid and, when implanted at the interventricular septal wall, could extend into contact with the cardiac tissue of a ventricular free wall or the tricuspid valve. The long and rigid body of existing leadless pacemakers could also become tangled within chordae tendinae. Furthermore, a proximal end of the existing leadless pacemakers may flail within the heart chamber as the heart beats, causing cyclical contact with adjacent heart structures. Such contact could interfere with heart function.

A leadless biostimulator that can be engaged to the interventricular septal wall, e.g., within a right ventricle, to pace the LBB without interfering with adjacent structures of the heart may include a flexible extended electrode. The flexible extension electrode can extend from a biostimulator housing to allow a pacing electrode to be located at an upper region of a septal wall. A housing of the biostimulator may be located near an apex of the right ventricle. Transportation to or from the right ventricle can be facilitated by a biostimulator transport system, as described below.

The present invention is defined in the independent claim. Further embodiments of the invention are defined in the dependent claims.

A biostimulator transport system is described. The biostimulator transport system includes a sleeve having a sleeve lumen, a support member extending through the sleeve lumen to a distal member end, and a belt extending longitudinally through the sleeve lumen between the sleeve and the support member. The belt can extend to a loop distal to the distal member end. For example, the loop can be a portion of the belt at which belt legs extend proximally back along the support member. The loop can define a gap between a socket of the support member at the distal member end and the belt.

A biostimulator system is also described. The biostimulator system includes a biostimulator, and the biostimulator transport system. The biostimulator includes a pacing electrode electrically connected to pacing circuitry contained within a housing of the biostimulator. A portion of the biostimulator, e.g., an articulation of a flexible extension electrode, can pass through the loop between the belt and the distal member end. The belt can be moved, e.g., by a drive mechanism, to spin the biostimulator within the socket at the distal member end. The pacing electrode of the biostimulator may be screwed into a target tissue when the biostimulator is rotated by the belt with the pacing electrode engaged to the target tissue.

The above summary does not include an exhaustive list of all aspects of the present description. It is contemplated that the description includes all systems that can be practiced from all suitable combinations of the various aspects summarized above, as well as those disclosed in the Detailed Description below and particularly pointed out in the claims. Such combinations have particular advantages not specifically recited in the above summary.

A better understanding of the features and advantages of the present invention will be obtained by reference to the following detailed description that sets forth illustrative embodiments, in which the principles of the invention are utilized, and the accompanying drawings.

Embodiments describe a biostimulator transport system and a biostimulator system for septal pacing. The biostimulator transport system and the biostimulator system may, however, be used in other applications, such as deep brain stimulation. Thus, reference to use of the biostimulator transport system or the biostimulator system for cardiac treatment is not limiting.

In various embodiments, description is made with reference to the figures. However, certain embodiments may be practiced without one or more of these specific details, or in combination with other known methods and configurations. In the following description, numerous specific details are set forth, such as specific configurations, dimensions, and processes, in order to provide a thorough understanding of the embodiments. In other instances, well-known processes and manufacturing techniques have not been described in particular detail in order to not unnecessarily obscure the description. Reference throughout this specification to "one embodiment," "an embodiment," or the like, means that a particular feature, structure, configuration, or characteristic described is included in at least one embodiment. Thus, the appearance of the phrase "one embodiment," "an embodiment," or the like, in various places throughout this specification are not necessarily referring to the same embodiment. Furthermore, the particular features, structures, configurations, or characteristics may be combined in any suitable manner in one or more embodiments.

The use of relative terms throughout the description may denote a relative position or direction. For example, "distal" may indicate a first direction along a longitudinal axis of a biostimulator transport system. Similarly, "proximal" may indicate a second direction opposite to the first direction. Such terms are provided to establish relative frames of reference, however, and are not intended to limit the use or orientation of a biostimulator transport system to a specific configuration described in the various embodiments below.

In an aspect, a biostimulator transport system is adapted to deliver and implant a leadless biostimulator. The biostimulator transport system can include a drive belt to retain the biostimulator during transport and to turn a portion of the biostimulator to drive a pacing electrode of the biostimulator into a target tissue. More particularly, the drive belt can be actuated to rotate the pacing electrode into the target tissue. The belt can be cut to release the biostimulator. Accordingly, the biostimulator can be placed with the pacing electrode in an upper region of a septal wall, and a housing of the biostimulator located near an apex of the right ventricle.

Referring to <FIG>, a diagrammatic cross-section of a patient heart illustrating an example implantation of a biostimulator in a target anatomy is shown in accordance with an embodiment. A biostimulator system, e.g., a leadless cardiac pacing system, includes one or more biostimulators <NUM>. The biostimulators <NUM> can be implanted in a patient heart <NUM>, and can be leadless (and thus, may be leadless cardiac pacemakers). Each biostimulator <NUM> can be placed in a cardiac chamber, such as a right atrium and/or right ventricle of the heart <NUM>, or attached to an inside or outside of the cardiac chamber. For example, the biostimulator <NUM> can be attached to one or more of an interventricular septal wall <NUM> or a ventricular apex <NUM> of the heart <NUM>. More particularly, the biostimulator <NUM> can be delivered to the septum, and one or more elements, such as a pacing electrode <NUM>, can pierce the interventricular septal wall <NUM> of the septum to engage and anchor the biostimulator <NUM> to the tissue. Similarly, a housing <NUM> and/or an anchor <NUM> can be delivered into the ventricular apex <NUM>.

The pacing electrode <NUM> can include a helical fixation element having an electrode axis <NUM>. The axis can be directed toward, e.g., normal to, the septal wall when the pacing electrode <NUM> is affixed to the septal wall. Similarly, the housing <NUM> can have a housing axis <NUM>, which is directed toward, e.g., oblique to, an apex wall of the ventricular apex <NUM> when the housing <NUM> is located therein. When the pacing electrode <NUM> is affixed to the interventricular septal wall <NUM>, and the housing <NUM> is located at the ventricular apex <NUM>, the electrode axis <NUM> can extend in a different direction than the housing axis <NUM>. For example, the electrode axis <NUM> can extend in a direction that is transverse or oblique to a direction of the housing axis <NUM>. The pacing electrode <NUM> can be electrically connected to pacing circuitry contained within the housing <NUM> of the biostimulator <NUM>. Accordingly, the pacing electrode <NUM> can be located to effectively probe and pace the left bundle branch, while the housing <NUM> can be placed in a safe and non-obstructive location within the heart chamber.

The non-coaxial relationship of the electrode axis <NUM> and the housing axis <NUM> can allow for safe and non-obstructive placement of the pacing electrode <NUM> and the housing <NUM>. The non-coaxial relationship may be provided by an articulation <NUM> of the biostimulator <NUM>. The articulation <NUM> can be located between the pacing electrode <NUM> and the housing <NUM>. For example, the articulation <NUM> may be a flexible portion of a lead extension, a hinge, or any other mechanism that acts as a joint or juncture between a distal portion and a proximal portion of the biostimulator. More particularly, the articulation <NUM> may provide a movable joint between the portions to allow the biostimulator to articulate and conform to the target anatomy.

Leadless pacemakers or other leadless biostimulators can be delivered to or retrieved from a patient using a transport system, e.g., a delivery or retrieval system. The transport system can include catheter-based transport systems used to deliver or retrieve a leadless biostimulator intravenously to or from a patient anatomy. Examples of biostimulator transport systems are described below. In some implementations of biostimulator systems, a biostimulator such as a leadless pacemaker is attached, connected to, or otherwise mounted on a distal end of a catheter of the biostimulator transport system. The leadless pacemaker is thereby advanced intravenously into or out of the heart <NUM>. The biostimulator transport system can include features to engage the leadless pacemaker to allow fixation of the leadless pacemaker to tissue. For example, in implementations where the leadless pacemaker includes an active engaging mechanism, such as a helical fixation element, the biostimulator transport system can include a drive belt configured to engage a portion of the leadless pacemaker and apply torque to screw the active engaging mechanism into or out of the tissue.

When the biostimulator <NUM> is delivered to and screwed into the septum of the heart <NUM>, the pacing electrode <NUM> may be positioned for deep septal pacing of a target tissue <NUM>, e.g., a target bundle branch in the septum. For example, an active electrode of the pacing element can be positioned at the left bundle branch in the septum. The biostimulator <NUM> may deliver pacing impulses through the pacing electrode <NUM> to the bundle branch(es).

Referring to <FIG>, a perspective view of a biostimulator system is shown in accordance with an embodiment. The biostimulator system <NUM> can include a biostimulator transport system <NUM>. The biostimulator transport system <NUM> can include a handle <NUM> to control movement and operations of the transport system from outside of a patient anatomy. One or more elongated members extend distally from the handle <NUM>. For example, a support member <NUM> can extend distally from the handle <NUM>. The support member <NUM> can extend to a distal end of the transport system <NUM>. In an embodiment, the biostimulator <NUM> is mounted on the biostimulator transport system <NUM>, e.g., at a distal end of one of the support member <NUM>.

The biostimulator transport system <NUM> can include a protective sleeve <NUM> to cover the biostimulator <NUM> during delivery and implantation. The protective sleeve <NUM> can extend over, and be longitudinally movable relative to, the support member <NUM>. The biostimulator transport system <NUM> may also include an introducer sheath <NUM> that can extend over, and be longitudinally movable relative to, the protective sleeve <NUM>. The introducer sheath <NUM> can cover a distal end of the protective sleeve <NUM>, the support member <NUM>, and the biostimulator <NUM> as those components are passed through an access device into the patient anatomy.

Several components of the biostimulator transport system <NUM> are described above by way of example. It will be appreciated, however, that the biostimulator transport system <NUM> may be configured to include additional or alternate components. More particularly, the biostimulator transport system <NUM> may be configured to deliver and/or retrieve the biostimulator <NUM> to or from the target anatomy. Delivery and/or retrieval of the biostimulator <NUM> can include retaining the biostimulator <NUM> during transport to the target anatomy and rotation of the biostimulator <NUM> during implantation of the biostimulator at the target anatomy. Accordingly, as described below, the biostimulator transport system <NUM> can incorporate features to retain and rotate the biostimulator <NUM>.

Referring to <FIG>, a cross-sectional view of a biostimulator retained within an extended sleeve of a biostimulator transport system is shown in accordance with an embodiment. The biostimulator transport system <NUM> can store and retain the biostimulator <NUM> within the sleeve <NUM> during transport to a target anatomy. More particularly, the sleeve <NUM> can include a sleeve lumen <NUM>, and the biostimulator <NUM> may be disposed within the sleeve lumen <NUM> during delivery and/or retrieval to/from the target anatomy. The sleeve <NUM> can include an elongated tubular member extending from a proximal sleeve end (not shown) to a distal sleeve end <NUM>. The sleeve lumen <NUM> can extend centrally through a length of the sleeve <NUM>. The distal member end <NUM> can be a distal tip or face of the elongated shaft. A material, size, and shape of the sleeve <NUM> may be selected to provide sufficient column strength and/or flexibility to allow the sleeve <NUM> to be tracked through a vasculature to the target anatomy.

The biostimulator transport system <NUM> can include the support member <NUM> extending through the sleeve lumen <NUM>. The support member <NUM> may be an elongated shaft extending from a proximal member end (not shown) to a distal member end <NUM>. A material, size, and shape of the support member <NUM> may be selected to provide sufficient column strength and/or flexibility to allow the support member <NUM> to be tracked through the vasculature to the target anatomy.

In an embodiment, a belt <NUM> extends longitudinally through the sleeve lumen <NUM>. The belt <NUM> can be formed from a flexible material, such as an elastomeric material, and can be located between the sleeve <NUM> and the support member <NUM>. For example, a belt leg may extend longitudinally through the sleeve lumen <NUM> and be positioned laterally between the support member <NUM> and a wall of the sleeve <NUM>. The belt <NUM> can have a belt leg on either side of the support member <NUM>, e.g., a pair of belt legs diametrically opposed within the sleeve lumen <NUM>. The belt legs can extend between the sleeve <NUM> and the support member <NUM> to a loop <NUM> located distal to the distal member end <NUM>. A first belt leg can extend distally beyond the distal member end <NUM>. The belt leg can loop laterally through the sleeve lumen <NUM> to a second belt leg, which extends back proximally through the sleeve lumen <NUM>. The loop <NUM> can form a gap between the distal member end <NUM> and a rear-facing surface of the loop <NUM> of the belt <NUM>, distal to the distal member end <NUM>.

The biostimulator <NUM> can be retained within the sleeve lumen <NUM> by the belt <NUM>. More particularly, a portion of the biostimulator <NUM>, e.g., a portion of the biostimulator between the housing <NUM> and the pacing electrode <NUM>, can extend through the loop <NUM>. The portion may be the articulation <NUM> of the biostimulator <NUM>. The articulation <NUM> can be a flexible portion of a lead extension, for example. The belt <NUM> can be cinched to hold the portion of the biostimulator <NUM> against the distal member end <NUM> and retain the biostimulator <NUM> relative to the support member <NUM>.

Referring to <FIG>, a cross-sectional view, taken about line A-A of <FIG>, of a biostimulator transport system is shown in accordance with an embodiment. The belt <NUM> of the biostimulator transport system <NUM> can be guided within a track <NUM> of the support member <NUM>. The support member <NUM> may include a lateral surface <NUM> having the track <NUM>. For example, the lateral surface <NUM> can have a notch, groove, or another longitudinal depression within which the belt <NUM> can extend. More particularly, each belt leg of the belt <NUM> can extend longitudinally through respective tracks <NUM>. The tracks <NUM> may be diametrically opposed, on opposite lateral surfaces <NUM> of the support member <NUM>. Thus, the belt legs may be diametrically opposed within the sleeve lumen <NUM>. The belt <NUM> may have a rectangular cross-sectional area, as shown, or may have a differently shaped cross-sectional area such as a circular cross-sectional area.

The track <NUM> can maintain a position of the belt legs such that the loop <NUM> remains centered within the sleeve lumen <NUM> relative to the distal member end <NUM>. Accordingly, the loop <NUM> can pull the portion of the biostimulator <NUM>, e.g., the articulation <NUM>, directly against the distal member end <NUM>.

Referring to <FIG>, a cross-sectional view, taken about line B-B of <FIG>, of a biostimulator transport system is shown in accordance with an embodiment. In an embodiment, the loop <NUM> includes a gripping surface <NUM>. The gripping surface <NUM> can be the rear-facing surface partly defining the gap. The gripping surface <NUM> can include a rough surface, such as a knurled surface or a tread. Alternatively or additionally, the gripping surface <NUM> can include a tacky surface, such as a surface coated with a sticky coating. The gripping surface <NUM> can be on an interior of the belt <NUM> facing the distal member end <NUM>. Accordingly, the gripping surface <NUM> can be in contact with the biostimulator <NUM> when the belt <NUM> is cinched against the biostimulator <NUM> to retain the portion of the biostimulator <NUM> against the distal member end <NUM>.

The gripping surface <NUM> of the belt <NUM> can have a higher coefficient of friction than a surface of a socket <NUM>. The biostimulator <NUM> retained between the distal member end <NUM> and the belt <NUM> may therefore more easily slide against the socket <NUM> than against the belt <NUM>. More particularly, when the belt <NUM> is pulled over the biostimulator <NUM>, it can grip the biostimulator <NUM> to cause the biostimulator <NUM> to rotate between the belt <NUM> and the socket <NUM>. The belt <NUM> may therefore be used to drive rotation of the biostimulator <NUM>.

The socket <NUM> can receive the portion of the biostimulator <NUM>. The socket <NUM> can include a depression or a hollow that forms a holder for the biostimulator <NUM>. For example, the retained portion of the biostimulator <NUM> may be a portion of a flexible extension having a circular cross-section, and the socket <NUM> may have an arched or saddle-shaped depression that conforms to an outer surface of the flexible extension. Similarly, the belt <NUM> can conform to the outer surface of the flexible extension. Thus, the belt <NUM> may be cinched to circumferentially support and hold the biostimulator <NUM> against the distal member end <NUM>.

The support member <NUM> may have a lubricious surface to facilitate sliding of the belt <NUM> within the track <NUM>, and sliding of the biostimulator within the socket <NUM>. For example, the support member <NUM> may be fabricated from a material having low surface friction, e.g., polytetrafluoroethylene, may be coated with a lubricious coating, or may have a surface impregnated with a lubricious material. The smooth surface of the support member <NUM> can allow the belt <NUM> to move and be cinched with minimal resistance. The smooth surface can also allow the portion of the biostimulator <NUM>, e.g., the articulation <NUM>, to slide within the socket <NUM> during implantation of the biostimulator <NUM>.

Referring to <FIG>, a cross-sectional view of a biostimulator exposed from a retracted sleeve of a biostimulator transport system is shown in accordance with an embodiment. The sleeve <NUM> can be longitudinally movable relative to the support member <NUM>. Accordingly, the sleeve <NUM> may be retracted relative to the support member <NUM> to expose the biostimulator <NUM>. When the sleeve <NUM> is retracted and the biostimulator <NUM> is exposed, the pacing electrode <NUM> of the biostimulator <NUM> may be directed forward. More particularly, the electrode axis <NUM> may extend longitudinally parallel to a longitudinal axis of the sleeve <NUM> and the support member <NUM>. The housing <NUM> of the biostimulator <NUM>, on the other hand, may swing and/or drop downward. For example, the housing axis <NUM> can extend in a transverse direction, e.g., oblique or orthogonal to the electrode axis <NUM>. Note the difference in relative orientation between the electrode axis <NUM> and the housing axis <NUM> with respect to <FIG>. When the sleeve <NUM> is in an extended state and the biostimulator <NUM> is within the sleeve <NUM>, as shown in <FIG>, the electrode axis <NUM> can extend in a same direction as the housing axis <NUM> of the housing <NUM>. By contrast, when the sleeve <NUM> is in the retracted state and the biostimulator <NUM> is exposed from the sleeve <NUM>, as shown in <FIG>, the electrode axis <NUM> can extend in a different direction than the housing axis <NUM> of the housing <NUM>.

Referring to <FIG>, a top view of a biostimulator exposed from a retracted sleeve of a biostimulator transport system is shown in accordance with an embodiment. The biostimulator transport system <NUM> can include a drive mechanism <NUM> to drive rotation of the biostimulator <NUM> when the sleeve <NUM> is retracted and the biostimulator <NUM> is in the exposed state. In an embodiment, a handle <NUM> is coupled to the support member <NUM> and the belt <NUM>. The handle <NUM> can include the drive mechanism <NUM>, and the drive mechanism may be controlled to drive the belt <NUM> through the track <NUM>. For example, the drive mechanism <NUM> can include a knob on the handle <NUM>, which may be rotated by a user. The knob can engage the belt <NUM>, e.g., through one or more transmission components, such as a gear, a friction wheel, or another component. The belt <NUM> can extend through a length of the sleeve <NUM> and wrap around the drive mechanism <NUM> such that the drive mechanism actuates movement of the belt <NUM>. For example, rotation of the knob can cause the belt <NUM> to slide in the track <NUM>. An interior surface of the belt <NUM> can include the gripping surface <NUM>, e.g., a tread, such that sliding the belt <NUM> through the track <NUM> imparts friction to the biostimulator <NUM> and causes the biostimulator to spin against the socket <NUM> of the support member <NUM>.

Referring to <FIG>, a side view of a biostimulator exposed from a retracted sleeve of a biostimulator transport system is shown in accordance with an embodiment. Actuation of the drive mechanism <NUM> can cause the belt <NUM> to slide along the lateral surface <NUM> of the support member <NUM>. As shown, one of the belt legs can move proximally along the lateral surface <NUM>. The other belt leg, which is hidden behind the support member <NUM> in <FIG>, can move distally along an opposing lateral surface <NUM> of the support member <NUM>. Accordingly, the loop <NUM> of the belt <NUM> can move laterally (out of the page). The belt <NUM> can grip and twist the biostimulator <NUM>, causing the biostimulator to slidably rotate within the socket <NUM> of the support member <NUM>. In an embodiment, the portion of the biostimulator <NUM> that is rotated by the belt <NUM> includes an elongated flexible extension. The extension connects to the pacing electrode <NUM> and the housing <NUM> of the biostimulator <NUM>. Accordingly, rotation of the biostimulator <NUM> can cause a distal portion of the extension, which is connected to the pacing electrode <NUM>, to rotate about the electrode axis <NUM>. Similarly, a proximal portion of the extension, which is connected to the housing <NUM>, can rotate about the housing axis <NUM>. The socket <NUM> can have a curvature to direct the distal portion of the pacing electrode <NUM> forward toward the target anatomy. When the pacing electrode <NUM> is engaged to the target anatomy, rotation of the extension can screw the pacing electrode <NUM> into the target tissue <NUM>.

Referring to <FIG>, a flowchart of a method of implanting a biostimulator <NUM> for septal pacing is shown. Certain operations of the implantation method are illustrated in <FIG>. Accordingly, <FIG> are described in combination below.

Referring to <FIG>, a diagrammatic view of an operation of advancing a biostimulator toward a target site is shown. During the implantation procedure, at operation <NUM>, the biostimulator transport system <NUM> can be advanced to the target tissue <NUM>. More particularly, the biostimulator transport system <NUM> can carry the biostimulator <NUM> into the target heart chamber. When implantation is to be within the right ventricle, the biostimulator transport system <NUM> can be tracked through the inferior vena cava into the right atrium and across the tricuspid valve into the right ventricle. The distal end of the biostimulator transport system <NUM> can be steered toward a desired location of the septal wall <NUM>. For example, the target area may be in an upper region of the interventricular septal wall <NUM>.

Referring to <FIG>, a diagrammatic view of an operation of implanting a biostimulator at a target site is shown. At operation <NUM>, the sleeve <NUM> of the biostimulator transport system <NUM> is retracted to expose the biostimulator <NUM>. In the exposed state, the electrode axis <NUM> and the housing axis <NUM> can move from an aligned orientation (as shown in <FIG> and <FIG>) to a misaligned orientation (as shown in <FIG>). In the misaligned orientation, the electrode axis <NUM> may be directed toward the target tissue <NUM> and the housing axis <NUM> can be directed downward toward an apex of the heart chamber.

The pacing electrode <NUM> of the biostimulator <NUM> can be directed toward the target tissue <NUM>. For example, biostimulatorr transport system <NUM> can include a steering mechanism in the handle <NUM> to allow a user to deflect and/or steer the distal member end <NUM> toward the target tissue <NUM>. Steering may be achieved, for example, using a steering cable or by incorporating a fixed curve into the catheter. Other steering mechanisms may be used. When the catheter is steered, the pacing electrode <NUM> can be directed toward the target tissue <NUM>.

The pacing electrode <NUM> may be affixed to the target tissue <NUM>, e.g., the interventricular septum. In operation <NUM>, the drive mechanism <NUM> is actuated to drive the pacing electrode <NUM> into the target tissue <NUM>. Actuation of the drive mechanism <NUM> can include moving the belt <NUM>, e.g., by spinning a knob that drives the belt <NUM>, relative to the support member <NUM>. The belt <NUM> may grip and rotate the biostimulator <NUM> against the distal member end <NUM>, causing the belt <NUM> to turn the pacing electrode <NUM> of the biostimulator <NUM> into the target tissue <NUM>. More particularly, the knob on the handle <NUM> can be rotated to impart movement to the belt <NUM>, and thus, when a distal end of the biostimulator <NUM> is in contact with the septal wall <NUM>, torque can be transferred from the biostimulator transport system <NUM> to the biostimulator <NUM> to drive the pacing electrode <NUM> (which may include a fixation helix) into the target tissue <NUM>. The pacing electrode <NUM> and/or the fixation helix can be screwed into the tissue to a desired depth by rotating the helically-shaped electrode into the target tissue <NUM>. In an embodiment, the pacing electrode <NUM> may engage the tissue at a depth that allows effective pacing of the target bundle branch.

When the biostimulator <NUM> is implanted in the desired location, the biostimulator transport system <NUM> may release the biostimulator <NUM>. For example, at operation <NUM>, the belt <NUM> may be cut to release the biostimulator <NUM>. The biostimulator transport system <NUM> can incorporate a blade to perform the cutting, or a user may use a separate cutting tool, such as scissors, to cut the belt <NUM>. When the belt <NUM> is cut, the biostimulator transport system <NUM> can be retracted. The belt <NUM> will slide over and release from the biostimulator <NUM> during system retraction, and the biostimulator <NUM> can remain in position at the target tissue <NUM>. The biostimulator <NUM> may therefore remain in place to perform the pacing function.

Claim 1:
A biostimulator transport system (<NUM>), comprising:
a sleeve (<NUM>) having a sleeve lumen (<NUM>);
a support member (<NUM>) extending through the sleeve lumen (<NUM>) to a distal member end (<NUM>); and
a belt (<NUM>) having a first leg laterally between a first lateral surface of the support member (<NUM>) and the sleeve (<NUM>), and a second leg laterally between a second lateral surface of the support member (<NUM>) and the sleeve (<NUM>), wherein the first leg and the second leg extend longitudinally through the sleeve lumen (<NUM>) to a loop (<NUM>) distal to the distal member end (<NUM>), to retain a biostimulator between the belt (<NUM>) and the support member (<NUM>) within the sleeve lumen (<NUM>).